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	$36.90	3.424%	$38.1635	$38.16	$38.15	$38.20
Purchase #2	$32.78	13.836%	$37.3154	$37.32	$37.30	$37.30
Purchase #3	$35.72	6.705%	$38.115	$38.12	$38.10	$38.10
Purchase #4	$120.45	8.442%	$130.6184	$130.62	$130.60	$130.60
Purchase #5	$139.80	13.650%	$158.8827	$158.88	$158.90	$158.90
Purchase #6	$98.58	5.700%	$104.1991	$104.20	$104.20	$104.20
Purchase #7	$15.25	13.157%	$17.2564	$17.26	$17.25	$17.30
7 purchase totals =	$479.48		$524.5505	$524.56	$524.50	$524.60