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 $168.62   5.690%   $178.2145   $178.21   $178.20   $178.20  
  Purchase #2 $56.70   5.195%   $59.6456   $59.65   $59.65   $59.60  
  Purchase #3 $59.28   11.473%   $66.0812   $66.08   $66.10   $66.10  
  Purchase #4 $226.25   6.790%   $241.6124   $241.61   $241.60   $241.60  
  Purchase #5 $210.97   8.191%   $228.2506   $228.25   $228.25   $228.30  
  Purchase #6 $152.62   7.282%   $163.7338   $163.73   $163.75   $163.70  
  Purchase #7 $111.29   13.285%   $126.0749   $126.07   $126.05   $126.10  
  7 purchase totals = $985.73       $1,063.6130   $1,063.60   $1,063.60   $1,063.60