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 $147.84   8.718%   $160.7287   $160.73   $160.75   $160.70  
  Purchase #2 $214.79   9.192%   $234.5335   $234.53   $234.55   $234.50  
  Purchase #3 $208.32   4.867%   $218.4589   $218.46   $218.45   $218.50  
  Purchase #4 $90.56   13.623%   $102.897   $102.90   $102.90   $102.90  
  Purchase #5 $209.52   11.336%   $233.2712   $233.27   $233.25   $233.30  
  Purchase #6 $185.59   9.752%   $203.6887   $203.69   $203.70   $203.70  
  Purchase #7 $12.86   9.199%   $14.043   $14.04   $14.05   $14.00  
  7 purchase totals = $1,069.48       $1,167.6210   $1,167.62   $1,167.65   $1,167.60