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 $194.57   5.854%   $205.9601   $205.96   $205.95   $206.00  
  Purchase #2 $92.97   3.322%   $96.0585   $96.06   $96.05   $96.10  
  Purchase #3 $150.87   3.132%   $155.5952   $155.60   $155.60   $155.60  
  Purchase #4 $50.31   9.721%   $55.2006   $55.20   $55.20   $55.20  
  Purchase #5 $219.32   12.264%   $246.2174   $246.22   $246.20   $246.20  
  Purchase #6 $233.99   11.371%   $260.597   $260.60   $260.60   $260.60  
  Purchase #7 $211.35   4.601%   $221.0742   $221.07   $221.05   $221.10  
  7 purchase totals = $1,153.38       $1,240.7030   $1,240.71   $1,240.65   $1,240.80