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	$146.61	6.326%	$155.8845	$155.88	$155.90	$155.90
Purchase #2	$70.42	9.674%	$77.2324	$77.23	$77.25	$77.20
Purchase #3	$85.87	8.323%	$93.017	$93.02	$93.00	$93.00
Purchase #4	$66.75	6.809%	$71.295	$71.30	$71.30	$71.30
Purchase #5	$107.93	3.719%	$111.9439	$111.94	$111.95	$111.90
Purchase #6	$155.65	6.596%	$165.9167	$165.92	$165.90	$165.90
Purchase #7	$210.46	5.534%	$222.1069	$222.11	$222.10	$222.10
7 purchase totals =	$843.69		$897.3964	$897.40	$897.40	$897.30