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 $196.49   7.540%   $211.3053   $211.31   $211.30   $211.30  
  Purchase #2 $232.98   4.696%   $243.9207   $243.92   $243.90   $243.90  
  Purchase #3 $177.56   11.682%   $198.3026   $198.30   $198.30   $198.30  
  Purchase #4 $114.92   7.864%   $123.9573   $123.96   $123.95   $124.00  
  Purchase #5 $78.60   9.272%   $85.8878   $85.89   $85.90   $85.90  
  Purchase #6 $105.28   11.108%   $116.9745   $116.97   $116.95   $117.00  
  Purchase #7 $75.95   5.133%   $79.8485   $79.85   $79.85   $79.80  
  7 purchase totals = $981.78       $1,060.1967   $1,060.20   $1,060.15   $1,060.20