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 $212.81   6.527%   $226.7001   $226.70   $226.70   $226.70  
  Purchase #2 $28.29   5.625%   $29.8813   $29.88   $29.90   $29.90  
  Purchase #3 $24.38   6.483%   $25.9606   $25.96   $25.95   $26.00  
  Purchase #4 $243.63   10.298%   $268.719   $268.72   $268.70   $268.70  
  Purchase #5 $185.67   8.563%   $201.5689   $201.57   $201.55   $201.60  
  Purchase #6 $189.39   5.727%   $200.2364   $200.24   $200.25   $200.20  
  Purchase #7 $186.71   6.112%   $198.1217   $198.12   $198.10   $198.10  
  7 purchase totals = $1,070.88       $1,151.1880   $1,151.19   $1,151.15   $1,151.20