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 $176.77   10.323%   $195.018   $195.02   $195.00   $195.00  
  Purchase #2 $29.48   7.874%   $31.8013   $31.80   $31.80   $31.80  
  Purchase #3 $67.27   10.844%   $74.5648   $74.56   $74.55   $74.60  
  Purchase #4 $217.95   10.478%   $240.7868   $240.79   $240.80   $240.80  
  Purchase #5 $128.30   9.565%   $140.5719   $140.57   $140.55   $140.60  
  Purchase #6 $200.70   5.452%   $211.6422   $211.64   $211.65   $211.60  
  Purchase #7 $149.78   4.590%   $156.6549   $156.65   $156.65   $156.70  
  7 purchase totals = $970.25       $1,051.0399   $1,051.03   $1,051.00   $1,051.10