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	$248.69	7.383%	$267.0508	$267.05	$267.05	$267.10
Purchase #2	$241.88	6.811%	$258.3544	$258.35	$258.35	$258.40
Purchase #3	$184.33	12.220%	$206.8551	$206.86	$206.85	$206.90
Purchase #4	$52.25	13.548%	$59.3288	$59.33	$59.35	$59.30
Purchase #5	$144.73	9.744%	$158.8325	$158.83	$158.85	$158.80
Purchase #6	$9.44	11.766%	$10.5507	$10.55	$10.55	$10.60
Purchase #7	$225.27	12.864%	$254.2487	$254.25	$254.25	$254.20
7 purchase totals =	$1,106.59		$1,215.2210	$1,215.22	$1,215.25	$1,215.30