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	$78.37	11.573%	$87.4398	$87.44	$87.45	$87.40
Purchase #2	$142.76	5.792%	$151.0287	$151.03	$151.05	$151.00
Purchase #3	$124.33	3.270%	$128.3956	$128.40	$128.40	$128.40
Purchase #4	$238.26	6.430%	$253.5801	$253.58	$253.60	$253.60
Purchase #5	$100.91	10.319%	$111.3229	$111.32	$111.30	$111.30
Purchase #6	$195.70	4.530%	$204.5652	$204.57	$204.55	$204.60
Purchase #7	$17.73	4.148%	$18.4654	$18.47	$18.45	$18.50
7 purchase totals =	$898.06		$954.7977	$954.81	$954.80	$954.80