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	$199.64	12.834%	$225.2618	$225.26	$225.25	$225.30
Purchase #2	$121.96	10.871%	$135.2183	$135.22	$135.20	$135.20
Purchase #3	$81.43	5.228%	$85.6872	$85.69	$85.70	$85.70
Purchase #4	$116.54	10.449%	$128.7173	$128.72	$128.70	$128.70
Purchase #5	$59.68	9.805%	$65.5316	$65.53	$65.55	$65.50
Purchase #6	$190.37	13.452%	$215.9786	$215.98	$216.00	$216.00
Purchase #7	$146.30	6.706%	$156.1109	$156.11	$156.10	$156.10
7 purchase totals =	$915.92		$1,012.5057	$1,012.51	$1,012.50	$1,012.50