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	$54.53	10.259%	$60.1242	$60.12	$60.10	$60.10
Purchase #2	$43.37	10.559%	$47.9494	$47.95	$47.95	$47.90
Purchase #3	$238.36	11.625%	$266.0694	$266.07	$266.05	$266.10
Purchase #4	$196.45	4.680%	$205.6439	$205.64	$205.65	$205.60
Purchase #5	$77.54	6.755%	$82.7778	$82.78	$82.80	$82.80
Purchase #6	$176.52	12.755%	$199.0351	$199.04	$199.05	$199.00
Purchase #7	$143.95	11.456%	$160.4409	$160.44	$160.45	$160.40
7 purchase totals =	$930.72		$1,022.0407	$1,022.04	$1,022.05	$1,021.90