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	$175.75	12.855%	$198.3427	$198.34	$198.35	$198.30
Purchase #2	$48.27	8.820%	$52.5274	$52.53	$52.55	$52.50
Purchase #3	$146.56	13.304%	$166.0583	$166.06	$166.05	$166.10
Purchase #4	$127.71	3.618%	$132.3305	$132.33	$132.35	$132.30
Purchase #5	$179.77	4.414%	$187.705	$187.71	$187.70	$187.70
Purchase #6	$128.28	7.396%	$137.7676	$137.77	$137.75	$137.80
Purchase #7	$19.88	4.753%	$20.8249	$20.82	$20.80	$20.80
7 purchase totals =	$826.22		$895.5564	$895.56	$895.55	$895.50