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 $118.78   5.515%   $125.3307   $125.33   $125.35   $125.30  
  Purchase #2 $184.69   6.535%   $196.7595   $196.76   $196.75   $196.80  
  Purchase #3 $175.50   9.263%   $191.7566   $191.76   $191.75   $191.80  
  Purchase #4 $134.75   3.132%   $138.9704   $138.97   $138.95   $139.00  
  Purchase #5 $236.84   11.758%   $264.6876   $264.69   $264.70   $264.70  
  Purchase #6 $88.39   7.785%   $95.2712   $95.27   $95.25   $95.30  
  Purchase #7 $200.29   5.736%   $211.7786   $211.78   $211.80   $211.80  
  7 purchase totals = $1,139.24       $1,224.5546   $1,224.56   $1,224.55   $1,224.70