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 $213.78   10.581%   $236.4001   $236.40   $236.40   $236.40  
  Purchase #2 $60.45   6.753%   $64.5322   $64.53   $64.55   $64.50  
  Purchase #3 $33.97   10.737%   $37.6174   $37.62   $37.60   $37.60  
  Purchase #4 $232.78   4.733%   $243.7975   $243.80   $243.80   $243.80  
  Purchase #5 $176.28   11.779%   $197.044   $197.04   $197.05   $197.00  
  Purchase #6 $53.81   13.516%   $61.083   $61.08   $61.10   $61.10  
  Purchase #7 $160.37   8.604%   $174.1682   $174.17   $174.15   $174.20  
  7 purchase totals = $931.44       $1,014.6424   $1,014.64   $1,014.65   $1,014.60