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	$146.89	11.205%	$163.349	$163.35	$163.35	$163.30
Purchase #2	$16.34	12.750%	$18.4234	$18.42	$18.40	$18.40
Purchase #3	$140.87	11.242%	$156.7066	$156.71	$156.70	$156.70
Purchase #4	$111.31	11.386%	$123.9838	$123.98	$124.00	$124.00
Purchase #5	$137.83	4.555%	$144.1082	$144.11	$144.10	$144.10
Purchase #6	$243.73	4.650%	$255.0634	$255.06	$255.05	$255.10
Purchase #7	$6.57	13.502%	$7.4571	$7.46	$7.45	$7.50
7 purchase totals =	$803.54		$869.0915	$869.09	$869.05	$869.10