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 $87.40   9.636%   $95.8219   $95.82   $95.80   $95.80  
  Purchase #2 $55.64   11.348%   $61.954   $61.95   $61.95   $62.00  
  Purchase #3 $26.71   6.226%   $28.373   $28.37   $28.35   $28.40  
  Purchase #4 $193.87   9.328%   $211.9542   $211.95   $211.95   $212.00  
  Purchase #5 $162.93   4.473%   $170.2179   $170.22   $170.20   $170.20  
  Purchase #6 $203.89   9.363%   $222.9802   $222.98   $223.00   $223.00  
  Purchase #7 $172.37   3.238%   $177.9513   $177.95   $177.95   $178.00  
  7 purchase totals = $902.81       $969.2525   $969.24   $969.20   $969.40