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	$54.42	9.770%	$59.7368	$59.74	$59.75	$59.70
Purchase #2	$36.99	13.174%	$41.8631	$41.86	$41.85	$41.90
Purchase #3	$91.36	9.382%	$99.9314	$99.93	$99.95	$99.90
Purchase #4	$12.56	12.291%	$14.1037	$14.10	$14.10	$14.10
Purchase #5	$235.96	3.461%	$244.1266	$244.13	$244.15	$244.10
Purchase #6	$216.55	11.113%	$240.6152	$240.62	$240.60	$240.60
Purchase #7	$88.55	8.267%	$95.8704	$95.87	$95.85	$95.90
7 purchase totals =	$736.39		$796.2472	$796.25	$796.25	$796.20