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	$59.88	4.138%	$62.3578	$62.36	$62.35	$62.40
Purchase #2	$50.74	4.105%	$52.8229	$52.82	$52.80	$52.80
Purchase #3	$131.96	5.443%	$139.1426	$139.14	$139.15	$139.10
Purchase #4	$28.68	12.521%	$32.271	$32.27	$32.25	$32.30
Purchase #5	$162.59	12.494%	$182.904	$182.90	$182.90	$182.90
Purchase #6	$12.35	11.485%	$13.7684	$13.77	$13.75	$13.80
Purchase #7	$40.74	13.703%	$46.3226	$46.32	$46.30	$46.30
7 purchase totals =	$486.94		$529.5893	$529.58	$529.50	$529.60