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	$63.88	11.135%	$70.993	$70.99	$71.00	$71.00
Purchase #2	$43.68	3.733%	$45.3106	$45.31	$45.30	$45.30
Purchase #3	$75.56	10.367%	$83.3933	$83.39	$83.40	$83.40
Purchase #4	$144.62	4.187%	$150.6752	$150.68	$150.70	$150.70
Purchase #5	$85.33	10.346%	$94.1582	$94.16	$94.15	$94.20
Purchase #6	$80.64	13.610%	$91.6151	$91.62	$91.60	$91.60
Purchase #7	$218.90	11.675%	$244.4566	$244.46	$244.45	$244.50
7 purchase totals =	$712.61		$780.6020	$780.61	$780.60	$780.70