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	$143.72	5.269%	$151.2926	$151.29	$151.30	$151.30
Purchase #2	$132.28	11.166%	$147.0504	$147.05	$147.05	$147.10
Purchase #3	$53.44	11.262%	$59.4584	$59.46	$59.45	$59.50
Purchase #4	$18.50	8.679%	$20.1056	$20.11	$20.10	$20.10
Purchase #5	$197.82	9.199%	$216.0175	$216.02	$216.00	$216.00
Purchase #6	$64.75	7.841%	$69.827	$69.83	$69.85	$69.80
Purchase #7	$228.34	9.777%	$250.6648	$250.66	$250.65	$250.70
7 purchase totals =	$838.85		$914.4163	$914.42	$914.40	$914.50