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	$204.46	9.328%	$223.532	$223.53	$223.55	$223.50
Purchase #2	$60.59	6.827%	$64.7265	$64.73	$64.75	$64.70
Purchase #3	$37.72	12.662%	$42.4961	$42.50	$42.50	$42.50
Purchase #4	$177.52	9.483%	$194.3542	$194.35	$194.35	$194.40
Purchase #5	$131.85	11.487%	$146.9956	$147.00	$147.00	$147.00
Purchase #6	$121.46	4.586%	$127.0302	$127.03	$127.05	$127.00
Purchase #7	$6.28	13.343%	$7.1179	$7.12	$7.10	$7.10
7 purchase totals =	$739.88		$806.2525	$806.26	$806.30	$806.20