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	$246.85	4.812%	$258.7284	$258.73	$258.75	$258.70
Purchase #2	$78.84	5.568%	$83.2298	$83.23	$83.25	$83.20
Purchase #3	$48.74	12.490%	$54.8276	$54.83	$54.85	$54.80
Purchase #4	$58.33	10.488%	$64.4477	$64.45	$64.45	$64.40
Purchase #5	$219.88	10.413%	$242.7761	$242.78	$242.80	$242.80
Purchase #6	$75.72	10.245%	$83.4775	$83.48	$83.50	$83.50
Purchase #7	$188.27	5.739%	$199.0748	$199.07	$199.05	$199.10
7 purchase totals =	$916.63		$986.5619	$986.57	$986.65	$986.50