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	$149.27	9.130%	$162.8984	$162.90	$162.90	$162.90
Purchase #2	$18.45	9.331%	$20.1716	$20.17	$20.15	$20.20
Purchase #3	$89.35	4.757%	$93.6004	$93.60	$93.60	$93.60
Purchase #4	$168.25	12.170%	$188.726	$188.73	$188.75	$188.70
Purchase #5	$160.29	3.161%	$165.3568	$165.36	$165.35	$165.40
Purchase #6	$18.33	11.454%	$20.4295	$20.43	$20.45	$20.40
Purchase #7	$201.53	11.102%	$223.9039	$223.90	$223.90	$223.90
7 purchase totals =	$805.47		$875.0866	$875.09	$875.10	$875.10