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	$189.63	13.479%	$215.1902	$215.19	$215.20	$215.20
Purchase #2	$53.47	4.280%	$55.7585	$55.76	$55.75	$55.80
Purchase #3	$31.65	6.467%	$33.6968	$33.70	$33.70	$33.70
Purchase #4	$68.84	4.589%	$71.9991	$72.00	$72.00	$72.00
Purchase #5	$37.68	12.527%	$42.4002	$42.40	$42.40	$42.40
Purchase #6	$100.86	10.766%	$111.7186	$111.72	$111.70	$111.70
Purchase #7	$14.69	11.533%	$16.3842	$16.38	$16.40	$16.40
7 purchase totals =	$496.82		$547.1476	$547.15	$547.15	$547.20