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	$244.75	12.706%	$275.8479	$275.85	$275.85	$275.80
Purchase #2	$167.75	13.205%	$189.9014	$189.90	$189.90	$189.90
Purchase #3	$56.51	6.681%	$60.2854	$60.29	$60.30	$60.30
Purchase #4	$225.36	8.650%	$244.8536	$244.85	$244.85	$244.90
Purchase #5	$62.94	5.672%	$66.51	$66.51	$66.50	$66.50
Purchase #6	$114.90	11.758%	$128.4099	$128.41	$128.40	$128.40
Purchase #7	$61.77	4.111%	$64.3094	$64.31	$64.30	$64.30
7 purchase totals =	$933.98		$1,030.1176	$1,030.12	$1,030.10	$1,030.10