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 $112.44   11.479%   $125.347   $125.35   $125.35   $125.30  
  Purchase #2 $180.73   11.690%   $201.8573   $201.86   $201.85   $201.90  
  Purchase #3 $148.38   11.869%   $165.9912   $165.99   $166.00   $166.00  
  Purchase #4 $173.92   3.415%   $179.8594   $179.86   $179.85   $179.90  
  Purchase #5 $57.29   6.233%   $60.8609   $60.86   $60.85   $60.90  
  Purchase #6 $245.30   5.819%   $259.574   $259.57   $259.55   $259.60  
  Purchase #7 $135.93   11.256%   $151.2303   $151.23   $151.25   $151.20  
  7 purchase totals = $1,053.99       $1,144.7201   $1,144.72   $1,144.70   $1,144.80