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	$117.52	8.478%	$127.4833	$127.48	$127.50	$127.50
Purchase #2	$164.75	11.286%	$183.3437	$183.34	$183.35	$183.30
Purchase #3	$130.31	13.262%	$147.5917	$147.59	$147.60	$147.60
Purchase #4	$27.59	8.269%	$29.8714	$29.87	$29.85	$29.90
Purchase #5	$50.61	5.719%	$53.5044	$53.50	$53.50	$53.50
Purchase #6	$30.52	12.726%	$34.404	$34.40	$34.40	$34.40
Purchase #7	$89.30	11.482%	$99.5534	$99.55	$99.55	$99.60
7 purchase totals =	$610.60		$675.7519	$675.73	$675.75	$675.80