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	$187.67	6.672%	$200.1913	$200.19	$200.20	$200.20
Purchase #2	$122.94	3.508%	$127.2527	$127.25	$127.25	$127.30
Purchase #3	$149.90	11.364%	$166.9346	$166.93	$166.95	$166.90
Purchase #4	$35.62	4.413%	$37.1919	$37.19	$37.20	$37.20
Purchase #5	$11.72	4.859%	$12.2895	$12.29	$12.30	$12.30
Purchase #6	$154.43	11.767%	$172.6018	$172.60	$172.60	$172.60
Purchase #7	$115.39	11.650%	$128.8329	$128.83	$128.85	$128.80
7 purchase totals =	$777.67		$845.2947	$845.28	$845.35	$845.30