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 $141.96   3.339%   $146.7   $146.70   $146.70   $146.70  
  Purchase #2 $202.33   7.668%   $217.8447   $217.84   $217.85   $217.80  
  Purchase #3 $8.37   6.265%   $8.8944   $8.89   $8.90   $8.90  
  Purchase #4 $185.67   10.649%   $205.442   $205.44   $205.45   $205.40  
  Purchase #5 $227.48   3.492%   $235.4236   $235.42   $235.40   $235.40  
  Purchase #6 $223.70   13.564%   $254.0427   $254.04   $254.05   $254.00  
  Purchase #7 $24.99   8.131%   $27.0219   $27.02   $27.00   $27.00  
  7 purchase totals = $1,014.50       $1,095.3693   $1,095.35   $1,095.35   $1,095.20