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	$144.94	7.355%	$155.6003	$155.60	$155.60	$155.60
Purchase #2	$233.64	13.397%	$264.9408	$264.94	$264.95	$264.90
Purchase #3	$99.26	12.304%	$111.473	$111.47	$111.45	$111.50
Purchase #4	$53.59	13.203%	$60.6655	$60.67	$60.65	$60.70
Purchase #5	$233.97	8.413%	$253.6539	$253.65	$253.65	$253.70
Purchase #6	$111.79	7.107%	$119.7349	$119.73	$119.75	$119.70
Purchase #7	$131.73	4.426%	$137.5604	$137.56	$137.55	$137.60
7 purchase totals =	$1,008.92		$1,103.6288	$1,103.62	$1,103.60	$1,103.70