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 $85.27   11.454%   $95.0368   $95.04   $95.05   $95.00  
  Purchase #2 $22.73   10.618%   $25.1435   $25.14   $25.15   $25.10  
  Purchase #3 $177.97   9.244%   $194.4215   $194.42   $194.40   $194.40  
  Purchase #4 $181.94   4.342%   $189.8398   $189.84   $189.85   $189.80  
  Purchase #5 $205.33   8.751%   $223.2984   $223.30   $223.30   $223.30  
  Purchase #6 $50.92   4.600%   $53.2623   $53.26   $53.25   $53.30  
  Purchase #7 $150.79   7.331%   $161.8444   $161.84   $161.85   $161.80  
  7 purchase totals = $874.95       $942.8467   $942.84   $942.85   $942.70