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 $211.69   5.631%   $223.6103   $223.61   $223.60   $223.60  
  Purchase #2 $222.59   7.224%   $238.6699   $238.67   $238.65   $238.70  
  Purchase #3 $43.98   9.859%   $48.316   $48.32   $48.30   $48.30  
  Purchase #4 $167.59   12.199%   $188.0343   $188.03   $188.05   $188.00  
  Purchase #5 $103.79   3.738%   $107.6697   $107.67   $107.65   $107.70  
  Purchase #6 $159.65   11.240%   $177.5947   $177.59   $177.60   $177.60  
  Purchase #7 $45.68   12.845%   $51.5476   $51.55   $51.55   $51.50  
  7 purchase totals = $954.97       $1,035.4425   $1,035.44   $1,035.40   $1,035.40