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	$244.59	4.306%	$255.122	$255.12	$255.10	$255.10
Purchase #2	$85.93	3.755%	$89.1567	$89.16	$89.15	$89.20
Purchase #3	$56.27	10.672%	$62.2751	$62.28	$62.30	$62.30
Purchase #4	$70.28	6.818%	$75.0717	$75.07	$75.05	$75.10
Purchase #5	$155.68	9.474%	$170.4291	$170.43	$170.45	$170.40
Purchase #6	$149.37	4.811%	$156.5562	$156.56	$156.55	$156.60
Purchase #7	$17.94	8.806%	$19.5198	$19.52	$19.50	$19.50
7 purchase totals =	$780.06		$828.1306	$828.14	$828.10	$828.20