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 $162.78   11.572%   $181.6169   $181.62   $181.60   $181.60  
  Purchase #2 $238.83   6.622%   $254.6453   $254.65   $254.65   $254.60  
  Purchase #3 $10.62   3.108%   $10.9501   $10.95   $10.95   $11.00  
  Purchase #4 $151.59   11.352%   $168.7985   $168.80   $168.80   $168.80  
  Purchase #5 $79.55   6.278%   $84.5441   $84.54   $84.55   $84.50  
  Purchase #6 $192.50   10.207%   $212.1485   $212.15   $212.15   $212.10  
  Purchase #7 $95.97   8.150%   $103.7916   $103.79   $103.80   $103.80  
  7 purchase totals = $931.84       $1,016.4950   $1,016.50   $1,016.50   $1,016.40