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 $125.68   6.481%   $133.8253   $133.83   $133.85   $133.80  
  Purchase #2 $203.29   4.758%   $212.9625   $212.96   $212.95   $213.00  
  Purchase #3 $160.43   13.429%   $181.9741   $181.97   $181.95   $182.00  
  Purchase #4 $199.95   9.431%   $218.8073   $218.81   $218.80   $218.80  
  Purchase #5 $105.94   11.737%   $118.3742   $118.37   $118.35   $118.40  
  Purchase #6 $47.59   4.157%   $49.5683   $49.57   $49.55   $49.60  
  Purchase #7 $205.72   6.410%   $218.9067   $218.91   $218.90   $218.90  
  7 purchase totals = $1,048.60       $1,134.4184   $1,134.42   $1,134.35   $1,134.50