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 $58.65   5.115%   $61.6499   $61.65   $61.65   $61.60  
  Purchase #2 $66.44   11.474%   $74.0633   $74.06   $74.05   $74.10  
  Purchase #3 $70.31   12.656%   $79.2084   $79.21   $79.20   $79.20  
  Purchase #4 $216.84   13.626%   $246.3866   $246.39   $246.40   $246.40  
  Purchase #5 $159.57   4.644%   $166.9804   $166.98   $167.00   $167.00  
  Purchase #6 $208.53   7.116%   $223.369   $223.37   $223.35   $223.40  
  Purchase #7 $238.38   13.391%   $270.3015   $270.30   $270.30   $270.30  
  7 purchase totals = $1,018.72       $1,121.9591   $1,121.96   $1,121.95   $1,122.00