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 $65.93   12.346%   $74.0697   $74.07   $74.05   $74.10  
  Purchase #2 $185.39   5.363%   $195.3325   $195.33   $195.35   $195.30  
  Purchase #3 $13.33   12.268%   $14.9653   $14.97   $14.95   $15.00  
  Purchase #4 $196.71   12.797%   $221.883   $221.88   $221.90   $221.90  
  Purchase #5 $22.35   7.838%   $24.1018   $24.10   $24.10   $24.10  
  Purchase #6 $235.41   13.453%   $267.0797   $267.08   $267.10   $267.10  
  Purchase #7 $244.52   6.542%   $260.5165   $260.52   $260.50   $260.50  
  7 purchase totals = $963.64       $1,057.9485   $1,057.95   $1,057.95   $1,058.00