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	$204.42	13.443%	$231.9002	$231.90	$231.90	$231.90
Purchase #2	$136.44	8.866%	$148.5368	$148.54	$148.55	$148.50
Purchase #3	$214.62	10.483%	$237.1186	$237.12	$237.10	$237.10
Purchase #4	$151.87	7.253%	$162.8851	$162.89	$162.90	$162.90
Purchase #5	$191.86	4.456%	$200.4093	$200.41	$200.40	$200.40
Purchase #6	$175.46	11.741%	$196.0608	$196.06	$196.05	$196.10
Purchase #7	$144.66	7.472%	$155.469	$155.47	$155.45	$155.50
7 purchase totals =	$1,219.33		$1,332.3798	$1,332.39	$1,332.35	$1,332.40