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	$128.46	10.147%	$141.4948	$141.49	$141.50	$141.50
Purchase #2	$110.74	8.142%	$119.7565	$119.76	$119.75	$119.80
Purchase #3	$136.74	11.257%	$152.1328	$152.13	$152.15	$152.10
Purchase #4	$144.38	5.122%	$151.7751	$151.78	$151.80	$151.80
Purchase #5	$230.62	12.183%	$258.7164	$258.72	$258.70	$258.70
Purchase #6	$109.49	7.152%	$117.3207	$117.32	$117.30	$117.30
Purchase #7	$61.96	8.538%	$67.2501	$67.25	$67.25	$67.30
7 purchase totals =	$922.39		$1,008.4464	$1,008.45	$1,008.45	$1,008.50