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	$78.64	6.747%	$83.9458	$83.95	$83.95	$83.90
Purchase #2	$61.98	13.132%	$70.1192	$70.12	$70.10	$70.10
Purchase #3	$17.67	10.412%	$19.5098	$19.51	$19.50	$19.50
Purchase #4	$150.78	3.273%	$155.715	$155.72	$155.70	$155.70
Purchase #5	$42.42	9.802%	$46.578	$46.58	$46.60	$46.60
Purchase #6	$13.66	11.399%	$15.2171	$15.22	$15.20	$15.20
Purchase #7	$142.36	7.816%	$153.4869	$153.49	$153.50	$153.50
7 purchase totals =	$507.51		$544.5718	$544.59	$544.55	$544.50