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	$185.45	5.689%	$196.0003	$196.00	$196.00	$196.00
Purchase #2	$13.84	8.483%	$15.014	$15.01	$15.00	$15.00
Purchase #3	$141.77	9.269%	$154.9107	$154.91	$154.90	$154.90
Purchase #4	$170.62	10.413%	$188.3867	$188.39	$188.40	$188.40
Purchase #5	$138.62	12.192%	$155.5206	$155.52	$155.50	$155.50
Purchase #6	$18.45	10.698%	$20.4238	$20.42	$20.40	$20.40
Purchase #7	$150.34	5.438%	$158.5155	$158.52	$158.50	$158.50
7 purchase totals =	$819.09		$888.7716	$888.77	$888.70	$888.70