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 $175.76   11.761%   $196.4311   $196.43   $196.45   $196.40  
  Purchase #2 $85.65   9.223%   $93.5495   $93.55   $93.55   $93.50  
  Purchase #3 $227.68   6.418%   $242.2925   $242.29   $242.30   $242.30  
  Purchase #4 $131.29   10.268%   $144.7709   $144.77   $144.75   $144.80  
  Purchase #5 $222.52   8.310%   $241.0114   $241.01   $241.00   $241.00  
  Purchase #6 $148.31   10.311%   $163.6022   $163.60   $163.60   $163.60  
  Purchase #7 $70.90   6.568%   $75.5567   $75.56   $75.55   $75.60  
  7 purchase totals = $1,062.11       $1,157.2143   $1,157.21   $1,157.20   $1,157.20