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 $43.65   8.525%   $47.3712   $47.37   $47.35   $47.40  
  Purchase #2 $175.25   9.262%   $191.4817   $191.48   $191.50   $191.50  
  Purchase #3 $173.34   4.339%   $180.8612   $180.86   $180.85   $180.90  
  Purchase #4 $134.29   11.292%   $149.454   $149.45   $149.45   $149.50  
  Purchase #5 $154.80   6.715%   $165.1948   $165.19   $165.20   $165.20  
  Purchase #6 $60.92   8.507%   $66.1025   $66.10   $66.10   $66.10  
  Purchase #7 $204.99   10.401%   $226.311   $226.31   $226.30   $226.30  
  7 purchase totals = $947.24       $1,026.7764   $1,026.76   $1,026.75   $1,026.90