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	$149.73	8.459%	$162.3957	$162.40	$162.40	$162.40
Purchase #2	$127.44	3.533%	$131.9425	$131.94	$131.95	$131.90
Purchase #3	$6.92	4.180%	$7.2093	$7.21	$7.20	$7.20
Purchase #4	$43.80	3.772%	$45.4521	$45.45	$45.45	$45.50
Purchase #5	$164.29	8.420%	$178.1232	$178.12	$178.10	$178.10
Purchase #6	$42.90	11.188%	$47.6997	$47.70	$47.70	$47.70
Purchase #7	$127.34	8.265%	$137.8647	$137.86	$137.85	$137.90
7 purchase totals =	$662.42		$710.6872	$710.68	$710.65	$710.70