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	$236.88	11.755%	$264.7252	$264.73	$264.75	$264.70
Purchase #2	$223.66	12.332%	$251.2418	$251.24	$251.25	$251.20
Purchase #3	$140.44	3.656%	$145.5745	$145.57	$145.55	$145.60
Purchase #4	$52.91	11.669%	$59.0841	$59.08	$59.10	$59.10
Purchase #5	$231.25	3.302%	$238.8859	$238.89	$238.90	$238.90
Purchase #6	$140.28	4.634%	$146.7806	$146.78	$146.80	$146.80
Purchase #7	$149.69	8.150%	$161.8897	$161.89	$161.90	$161.90
7 purchase totals =	$1,175.11		$1,268.1818	$1,268.18	$1,268.25	$1,268.20