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	$208.77	4.569%	$218.3087	$218.31	$218.30	$218.30
Purchase #2	$40.49	7.664%	$43.5932	$43.59	$43.60	$43.60
Purchase #3	$7.42	9.677%	$8.138	$8.14	$8.15	$8.10
Purchase #4	$32.52	3.802%	$33.7564	$33.76	$33.75	$33.80
Purchase #5	$28.31	3.821%	$29.3917	$29.39	$29.40	$29.40
Purchase #6	$241.53	13.574%	$274.3153	$274.32	$274.30	$274.30
Purchase #7	$124.25	10.181%	$136.8999	$136.90	$136.90	$136.90
7 purchase totals =	$683.29		$744.4032	$744.41	$744.40	$744.40