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	$153.99	7.416%	$165.4099	$165.41	$165.40	$165.40
Purchase #2	$143.40	11.317%	$159.6286	$159.63	$159.65	$159.60
Purchase #3	$199.83	6.363%	$212.5452	$212.55	$212.55	$212.50
Purchase #4	$54.52	9.560%	$59.7321	$59.73	$59.75	$59.70
Purchase #5	$188.85	8.193%	$204.3225	$204.32	$204.30	$204.30
Purchase #6	$221.99	10.611%	$245.5454	$245.55	$245.55	$245.50
Purchase #7	$148.70	3.229%	$153.5015	$153.50	$153.50	$153.50
7 purchase totals =	$1,111.28		$1,200.6852	$1,200.69	$1,200.70	$1,200.50