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	$214.30	3.847%	$222.5441	$222.54	$222.55	$222.50
Purchase #2	$196.53	10.301%	$216.7746	$216.77	$216.75	$216.80
Purchase #3	$22.46	12.601%	$25.2902	$25.29	$25.30	$25.30
Purchase #4	$93.82	10.502%	$103.673	$103.67	$103.65	$103.70
Purchase #5	$225.59	10.217%	$248.6385	$248.64	$248.65	$248.60
Purchase #6	$155.46	12.827%	$175.4009	$175.40	$175.40	$175.40
Purchase #7	$104.47	11.121%	$116.0881	$116.09	$116.10	$116.10
7 purchase totals =	$1,012.63		$1,108.4094	$1,108.40	$1,108.40	$1,108.40