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	$28.44	4.479%	$29.7138	$29.71	$29.70	$29.70
Purchase #2	$83.72	6.582%	$89.2305	$89.23	$89.25	$89.20
Purchase #3	$14.66	4.179%	$15.2726	$15.27	$15.25	$15.30
Purchase #4	$73.62	9.111%	$80.3275	$80.33	$80.35	$80.30
Purchase #5	$79.66	5.168%	$83.7768	$83.78	$83.80	$83.80
Purchase #6	$15.51	8.784%	$16.8724	$16.87	$16.85	$16.90
Purchase #7	$130.61	4.872%	$136.9733	$136.97	$136.95	$137.00
7 purchase totals =	$426.22		$452.1669	$452.16	$452.15	$452.20