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 $56.73   9.207%   $61.9531   $61.95   $61.95   $62.00  
  Purchase #2 $223.57   10.191%   $246.354   $246.35   $246.35   $246.40  
  Purchase #3 $225.67   3.176%   $232.8373   $232.84   $232.85   $232.80  
  Purchase #4 $112.70   13.243%   $127.6249   $127.62   $127.60   $127.60  
  Purchase #5 $84.90   12.751%   $95.7256   $95.73   $95.75   $95.70  
  Purchase #6 $125.52   4.731%   $131.4584   $131.46   $131.45   $131.50  
  Purchase #7 $214.59   11.194%   $238.6112   $238.61   $238.60   $238.60  
  7 purchase totals = $1,043.68       $1,134.5645   $1,134.56   $1,134.55   $1,134.60