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	$66.65	7.406%	$71.5861	$71.59	$71.60	$71.60
Purchase #2	$200.72	7.674%	$216.1233	$216.12	$216.10	$216.10
Purchase #3	$27.84	5.532%	$29.3801	$29.38	$29.40	$29.40
Purchase #4	$244.82	7.411%	$262.9636	$262.96	$262.95	$263.00
Purchase #5	$130.82	10.314%	$144.3128	$144.31	$144.30	$144.30
Purchase #6	$6.69	11.163%	$7.4368	$7.44	$7.45	$7.40
Purchase #7	$136.41	13.224%	$154.4489	$154.45	$154.45	$154.40
7 purchase totals =	$813.95		$886.2516	$886.25	$886.25	$886.20