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	$67.33	11.152%	$74.8386	$74.84	$74.85	$74.80
Purchase #2	$134.56	12.550%	$151.4473	$151.45	$151.45	$151.40
Purchase #3	$139.71	11.333%	$155.5433	$155.54	$155.55	$155.50
Purchase #4	$245.77	3.499%	$254.3695	$254.37	$254.35	$254.40
Purchase #5	$48.52	7.454%	$52.1367	$52.14	$52.15	$52.10
Purchase #6	$124.68	3.170%	$128.6324	$128.63	$128.65	$128.60
Purchase #7	$233.89	3.755%	$242.6726	$242.67	$242.65	$242.70
7 purchase totals =	$994.46		$1,059.6404	$1,059.64	$1,059.65	$1,059.50