Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $174.79   12.142%   $196.013   $196.01   $196.00   $196.00  
  Purchase #2 $96.36   11.818%   $107.7478   $107.75   $107.75   $107.70  
  Purchase #3 $191.71   9.590%   $210.095   $210.10   $210.10   $210.10  
  Purchase #4 $171.50   12.192%   $192.4093   $192.41   $192.40   $192.40  
  Purchase #5 $109.99   10.593%   $121.6412   $121.64   $121.65   $121.60  
  Purchase #6 $247.57   8.652%   $268.9898   $268.99   $269.00   $269.00  
  Purchase #7 $220.79   4.655%   $231.0678   $231.07   $231.05   $231.10  
  7 purchase totals = $1,212.71       $1,327.9639   $1,327.97   $1,327.95   $1,327.90