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	$240.45	9.125%	$262.3911	$262.39	$262.40	$262.40
Purchase #2	$135.63	6.361%	$144.2574	$144.26	$144.25	$144.30
Purchase #3	$130.89	11.124%	$145.4502	$145.45	$145.45	$145.50
Purchase #4	$77.88	13.559%	$88.4397	$88.44	$88.45	$88.40
Purchase #5	$211.88	5.415%	$223.3533	$223.35	$223.35	$223.40
Purchase #6	$31.40	10.705%	$34.7614	$34.76	$34.75	$34.80
Purchase #7	$228.27	12.346%	$256.4522	$256.45	$256.45	$256.50
7 purchase totals =	$1,056.40		$1,155.1053	$1,155.10	$1,155.10	$1,155.30