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 $67.34   3.280%   $69.5488   $69.55   $69.55   $69.50  
  Purchase #2 $195.37   4.551%   $204.2613   $204.26   $204.25   $204.30  
  Purchase #3 $14.54   9.833%   $15.9697   $15.97   $15.95   $16.00  
  Purchase #4 $75.30   3.250%   $77.7473   $77.75   $77.75   $77.70  
  Purchase #5 $179.94   4.392%   $187.843   $187.84   $187.85   $187.80  
  Purchase #6 $142.80   8.506%   $154.9466   $154.95   $154.95   $154.90  
  Purchase #7 $159.36   3.667%   $165.2037   $165.20   $165.20   $165.20  
  7 purchase totals = $834.65       $875.5204   $875.52   $875.50   $875.40