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 $88.52   7.327%   $95.0059   $95.01   $95.00   $95.00  
  Purchase #2 $118.47   5.246%   $124.6849   $124.68   $124.70   $124.70  
  Purchase #3 $29.71   9.190%   $32.4403   $32.44   $32.45   $32.40  
  Purchase #4 $67.30   3.392%   $69.5828   $69.58   $69.60   $69.60  
  Purchase #5 $120.64   11.127%   $134.0636   $134.06   $134.05   $134.10  
  Purchase #6 $5.29   9.308%   $5.7824   $5.78   $5.80   $5.80  
  Purchase #7 $104.88   5.312%   $110.4512   $110.45   $110.45   $110.50  
  7 purchase totals = $534.81       $572.0111   $572.00   $572.05   $572.10