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 $183.62   7.264%   $196.9582   $196.96   $196.95   $197.00  
  Purchase #2 $211.56   7.284%   $226.97   $226.97   $226.95   $227.00  
  Purchase #3 $41.75   4.129%   $43.4739   $43.47   $43.45   $43.50  
  Purchase #4 $96.65   10.479%   $106.778   $106.78   $106.80   $106.80  
  Purchase #5 $213.62   9.170%   $233.209   $233.21   $233.20   $233.20  
  Purchase #6 $128.67   6.550%   $137.0979   $137.10   $137.10   $137.10  
  Purchase #7 $246.92   11.180%   $274.5257   $274.53   $274.55   $274.50  
  7 purchase totals = $1,122.79       $1,219.0127   $1,219.02   $1,219.00   $1,219.10