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 $211.85   6.827%   $226.313   $226.31   $226.30   $226.30  
  Purchase #2 $162.54   6.678%   $173.3944   $173.39   $173.40   $173.40  
  Purchase #3 $232.65   6.249%   $247.1883   $247.19   $247.20   $247.20  
  Purchase #4 $235.83   8.808%   $256.6019   $256.60   $256.60   $256.60  
  Purchase #5 $25.52   7.206%   $27.359   $27.36   $27.35   $27.40  
  Purchase #6 $188.92   5.586%   $199.4731   $199.47   $199.45   $199.50  
  Purchase #7 $19.84   11.314%   $22.0847   $22.08   $22.10   $22.10  
  7 purchase totals = $1,077.15       $1,152.4144   $1,152.40   $1,152.40   $1,152.50