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 $64.72   10.819%   $71.7221   $71.72   $71.70   $71.70  
  Purchase #2 $192.76   12.107%   $216.0975   $216.10   $216.10   $216.10  
  Purchase #3 $59.67   9.439%   $65.3023   $65.30   $65.30   $65.30  
  Purchase #4 $186.35   8.548%   $202.2792   $202.28   $202.30   $202.30  
  Purchase #5 $194.80   6.420%   $207.3062   $207.31   $207.30   $207.30  
  Purchase #6 $196.93   13.613%   $223.7381   $223.74   $223.75   $223.70  
  Purchase #7 $54.26   11.118%   $60.2926   $60.29   $60.30   $60.30  
  7 purchase totals = $949.49       $1,046.7380   $1,046.74   $1,046.75   $1,046.70