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 $97.29   9.613%   $106.6425   $106.64   $106.65   $106.60  
  Purchase #2 $218.42   3.721%   $226.5474   $226.55   $226.55   $226.50  
  Purchase #3 $80.27   4.445%   $83.838   $83.84   $83.85   $83.80  
  Purchase #4 $125.64   5.530%   $132.5879   $132.59   $132.60   $132.60  
  Purchase #5 $198.68   6.631%   $211.8545   $211.85   $211.85   $211.90  
  Purchase #6 $64.97   11.577%   $72.4916   $72.49   $72.50   $72.50  
  Purchase #7 $206.64   6.310%   $219.679   $219.68   $219.70   $219.70  
  7 purchase totals = $991.91       $1,053.6409   $1,053.64   $1,053.70   $1,053.60