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	$215.33	13.662%	$244.7484	$244.75	$244.75	$244.70
Purchase #2	$191.91	4.564%	$200.6688	$200.67	$200.65	$200.70
Purchase #3	$37.25	10.651%	$41.2175	$41.22	$41.20	$41.20
Purchase #4	$173.96	10.237%	$191.7683	$191.77	$191.75	$191.80
Purchase #5	$38.43	6.363%	$40.8753	$40.88	$40.90	$40.90
Purchase #6	$173.39	3.245%	$179.0165	$179.02	$179.00	$179.00
Purchase #7	$97.37	9.267%	$106.3933	$106.39	$106.40	$106.40
7 purchase totals =	$927.64		$1,004.6881	$1,004.70	$1,004.65	$1,004.70