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 $182.36   11.654%   $203.6122   $203.61   $203.60   $203.60  
  Purchase #2 $191.45   6.270%   $203.4539   $203.45   $203.45   $203.50  
  Purchase #3 $219.89   3.530%   $227.6521   $227.65   $227.65   $227.70  
  Purchase #4 $136.27   4.170%   $141.9525   $141.95   $141.95   $142.00  
  Purchase #5 $118.65   9.393%   $129.7948   $129.79   $129.80   $129.80  
  Purchase #6 $181.96   11.842%   $203.5077   $203.51   $203.50   $203.50  
  Purchase #7 $77.74   6.159%   $82.528   $82.53   $82.55   $82.50  
  7 purchase totals = $1,108.32       $1,192.5012   $1,192.49   $1,192.50   $1,192.60