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	$53.36	10.702%	$59.0706	$59.07	$59.05	$59.10
Purchase #2	$214.86	7.159%	$230.2418	$230.24	$230.25	$230.20
Purchase #3	$45.82	10.116%	$50.4552	$50.46	$50.45	$50.50
Purchase #4	$28.67	12.223%	$32.1743	$32.17	$32.15	$32.20
Purchase #5	$94.44	11.708%	$105.497	$105.50	$105.50	$105.50
Purchase #6	$196.31	4.482%	$205.1086	$205.11	$205.10	$205.10
Purchase #7	$141.61	10.751%	$156.8345	$156.83	$156.85	$156.80
7 purchase totals =	$775.07		$839.3820	$839.38	$839.35	$839.40