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	$56.59	6.613%	$60.3323	$60.33	$60.35	$60.30
Purchase #2	$180.74	5.158%	$190.0626	$190.06	$190.05	$190.10
Purchase #3	$204.35	6.152%	$216.9216	$216.92	$216.90	$216.90
Purchase #4	$151.94	10.720%	$168.228	$168.23	$168.25	$168.20
Purchase #5	$229.54	13.830%	$261.2854	$261.29	$261.30	$261.30
Purchase #6	$65.30	11.711%	$72.9473	$72.95	$72.95	$72.90
Purchase #7	$146.38	8.261%	$158.4725	$158.47	$158.45	$158.50
7 purchase totals =	$1,034.84		$1,128.2497	$1,128.25	$1,128.25	$1,128.20