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	$75.76	4.111%	$78.8745	$78.87	$78.85	$78.90
Purchase #2	$149.28	10.560%	$165.044	$165.04	$165.05	$165.00
Purchase #3	$179.29	6.174%	$190.3594	$190.36	$190.35	$190.40
Purchase #4	$217.83	6.448%	$231.8757	$231.88	$231.90	$231.90
Purchase #5	$117.29	8.753%	$127.5564	$127.56	$127.55	$127.60
Purchase #6	$201.95	3.170%	$208.3518	$208.35	$208.35	$208.40
Purchase #7	$113.86	4.162%	$118.5989	$118.60	$118.60	$118.60
7 purchase totals =	$1,055.26		$1,120.6607	$1,120.66	$1,120.65	$1,120.80