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	$137.25	8.302%	$148.6445	$148.64	$148.65	$148.60
Purchase #2	$49.81	13.212%	$56.3909	$56.39	$56.40	$56.40
Purchase #3	$221.32	11.812%	$247.4623	$247.46	$247.45	$247.50
Purchase #4	$215.76	3.697%	$223.7366	$223.74	$223.75	$223.70
Purchase #5	$58.76	9.639%	$64.4239	$64.42	$64.40	$64.40
Purchase #6	$127.27	10.233%	$140.2935	$140.29	$140.30	$140.30
Purchase #7	$172.29	11.609%	$192.2911	$192.29	$192.30	$192.30
7 purchase totals =	$982.46		$1,073.2428	$1,073.23	$1,073.25	$1,073.20