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	$52.86	11.284%	$58.8247	$58.82	$58.80	$58.80
Purchase #2	$69.89	4.435%	$72.9896	$72.99	$73.00	$73.00
Purchase #3	$195.56	13.583%	$222.1229	$222.12	$222.10	$222.10
Purchase #4	$55.41	13.213%	$62.7313	$62.73	$62.75	$62.70
Purchase #5	$141.67	12.117%	$158.8362	$158.84	$158.85	$158.80
Purchase #6	$212.81	12.204%	$238.7813	$238.78	$238.80	$238.80
Purchase #7	$9.69	11.834%	$10.8367	$10.84	$10.85	$10.80
7 purchase totals =	$737.89		$825.1227	$825.12	$825.15	$825.00