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	$173.25	10.444%	$191.3442	$191.34	$191.35	$191.30
Purchase #2	$59.96	10.443%	$66.2216	$66.22	$66.20	$66.20
Purchase #3	$145.34	4.577%	$151.9922	$151.99	$152.00	$152.00
Purchase #4	$103.74	13.112%	$117.3424	$117.34	$117.35	$117.30
Purchase #5	$123.34	7.288%	$132.329	$132.33	$132.35	$132.30
Purchase #6	$91.65	9.655%	$100.4988	$100.50	$100.50	$100.50
Purchase #7	$64.66	9.345%	$70.7025	$70.70	$70.70	$70.70
7 purchase totals =	$761.94		$830.4307	$830.42	$830.45	$830.30