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	$229.79	10.135%	$253.0792	$253.08	$253.10	$253.10
Purchase #2	$247.67	12.263%	$278.0418	$278.04	$278.05	$278.00
Purchase #3	$37.69	9.236%	$41.171	$41.17	$41.15	$41.20
Purchase #4	$38.42	9.684%	$42.1406	$42.14	$42.15	$42.10
Purchase #5	$123.58	3.373%	$127.7484	$127.75	$127.75	$127.70
Purchase #6	$137.34	8.475%	$148.9796	$148.98	$149.00	$149.00
Purchase #7	$62.78	7.301%	$67.3636	$67.36	$67.35	$67.40
7 purchase totals =	$877.27		$958.5242	$958.52	$958.55	$958.50