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 $88.25   11.275%   $98.2002   $98.20   $98.20   $98.20  
  Purchase #2 $127.61   10.597%   $141.1328   $141.13   $141.15   $141.10  
  Purchase #3 $211.90   5.347%   $223.2303   $223.23   $223.25   $223.20  
  Purchase #4 $144.56   8.428%   $156.7435   $156.74   $156.75   $156.70  
  Purchase #5 $225.47   3.250%   $232.7978   $232.80   $232.80   $232.80  
  Purchase #6 $186.52   3.463%   $192.9792   $192.98   $193.00   $193.00  
  Purchase #7 $82.75   6.691%   $88.2868   $88.29   $88.30   $88.30  
  7 purchase totals = $1,067.06       $1,133.3706   $1,133.37   $1,133.45   $1,133.30