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	$141.67	7.621%	$152.4667	$152.47	$152.45	$152.50
Purchase #2	$31.50	9.277%	$34.4223	$34.42	$34.40	$34.40
Purchase #3	$83.64	12.750%	$94.3041	$94.30	$94.30	$94.30
Purchase #4	$170.81	7.175%	$183.0656	$183.07	$183.05	$183.10
Purchase #5	$98.73	12.472%	$111.0436	$111.04	$111.05	$111.00
Purchase #6	$82.97	8.352%	$89.8997	$89.90	$89.90	$89.90
Purchase #7	$233.74	7.530%	$251.3406	$251.34	$251.35	$251.30
7 purchase totals =	$843.06		$916.5426	$916.54	$916.50	$916.50