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 $224.78   5.546%   $237.2463   $237.25   $237.25   $237.20  
  Purchase #2 $228.96   7.793%   $246.8029   $246.80   $246.80   $246.80  
  Purchase #3 $12.32   6.270%   $13.0925   $13.09   $13.10   $13.10  
  Purchase #4 $70.57   9.494%   $77.2699   $77.27   $77.25   $77.30  
  Purchase #5 $69.69   8.494%   $75.6095   $75.61   $75.60   $75.60  
  Purchase #6 $94.58   11.282%   $105.2505   $105.25   $105.25   $105.30  
  Purchase #7 $91.84   5.470%   $96.8636   $96.86   $96.85   $96.90  
  7 purchase totals = $792.74       $852.1352   $852.13   $852.10   $852.20