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	$160.84	7.257%	$172.5122	$172.51	$172.50	$172.50
Purchase #2	$109.53	7.738%	$118.0054	$118.01	$118.00	$118.00
Purchase #3	$141.40	7.351%	$151.7943	$151.79	$151.80	$151.80
Purchase #4	$59.53	13.600%	$67.6261	$67.63	$67.65	$67.60
Purchase #5	$226.91	11.783%	$253.6468	$253.65	$253.65	$253.60
Purchase #6	$108.89	8.415%	$118.0531	$118.05	$118.05	$118.10
Purchase #7	$220.76	9.833%	$242.4673	$242.47	$242.45	$242.50
7 purchase totals =	$1,027.86		$1,124.1052	$1,124.11	$1,124.10	$1,124.10