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 $180.77   8.397%   $195.9493   $195.95   $195.95   $195.90  
  Purchase #2 $241.56   9.646%   $264.8609   $264.86   $264.85   $264.90  
  Purchase #3 $222.74   7.209%   $238.7973   $238.80   $238.80   $238.80  
  Purchase #4 $122.90   8.524%   $133.376   $133.38   $133.40   $133.40  
  Purchase #5 $63.54   3.465%   $65.7417   $65.74   $65.75   $65.70  
  Purchase #6 $52.39   8.758%   $56.9783   $56.98   $57.00   $57.00  
  Purchase #7 $211.55   6.512%   $225.3261   $225.33   $225.35   $225.30  
  7 purchase totals = $1,095.45       $1,181.0296   $1,181.04   $1,181.10   $1,181.00