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 $152.87   9.283%   $167.0609   $167.06   $167.05   $167.10  
  Purchase #2 $173.41   13.451%   $196.7354   $196.74   $196.75   $196.70  
  Purchase #3 $12.41   13.637%   $14.1024   $14.10   $14.10   $14.10  
  Purchase #4 $243.48   9.737%   $267.1876   $267.19   $267.20   $267.20  
  Purchase #5 $6.75   4.464%   $7.0513   $7.05   $7.05   $7.10  
  Purchase #6 $27.45   7.226%   $29.4335   $29.43   $29.45   $29.40  
  Purchase #7 $153.37   11.102%   $170.3971   $170.40   $170.40   $170.40  
  7 purchase totals = $769.74       $851.9682   $851.97   $852.00   $852.00