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 $65.33   11.351%   $72.7456   $72.75   $72.75   $72.70  
  Purchase #2 $161.98   8.639%   $175.9735   $175.97   $175.95   $176.00  
  Purchase #3 $150.91   12.213%   $169.3406   $169.34   $169.35   $169.30  
  Purchase #4 $101.98   4.330%   $106.3957   $106.40   $106.40   $106.40  
  Purchase #5 $130.99   7.813%   $141.2242   $141.22   $141.20   $141.20  
  Purchase #6 $203.64   11.574%   $227.2093   $227.21   $227.20   $227.20  
  Purchase #7 $138.48   12.156%   $155.3136   $155.31   $155.30   $155.30  
  7 purchase totals = $953.31       $1,048.2025   $1,048.20   $1,048.15   $1,048.10