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 $181.48   7.810%   $195.6536   $195.65   $195.65   $195.70  
  Purchase #2 $90.47   10.107%   $99.6138   $99.61   $99.60   $99.60  
  Purchase #3 $118.38   12.756%   $133.4806   $133.48   $133.50   $133.50  
  Purchase #4 $135.96   11.783%   $151.9802   $151.98   $152.00   $152.00  
  Purchase #5 $201.65   3.378%   $208.4617   $208.46   $208.45   $208.50  
  Purchase #6 $224.85   4.244%   $234.3926   $234.39   $234.40   $234.40  
  Purchase #7 $21.40   4.353%   $22.3315   $22.33   $22.35   $22.30  
  7 purchase totals = $974.19       $1,045.9140   $1,045.90   $1,045.95   $1,046.00