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	$51.30	8.658%	$55.7416	$55.74	$55.75	$55.70
Purchase #2	$223.32	11.135%	$248.1867	$248.19	$248.20	$248.20
Purchase #3	$238.61	3.234%	$246.3266	$246.33	$246.35	$246.30
Purchase #4	$138.54	8.596%	$150.4489	$150.45	$150.45	$150.40
Purchase #5	$88.26	13.659%	$100.3154	$100.32	$100.30	$100.30
Purchase #6	$85.77	7.863%	$92.5141	$92.51	$92.50	$92.50
Purchase #7	$236.65	5.472%	$249.5995	$249.60	$249.60	$249.60
7 purchase totals =	$1,062.45		$1,143.1328	$1,143.14	$1,143.15	$1,143.00