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	$98.55	13.519%	$111.873	$111.87	$111.85	$111.90
Purchase #2	$7.65	11.539%	$8.5327	$8.53	$8.55	$8.50
Purchase #3	$146.44	9.454%	$160.2844	$160.28	$160.30	$160.30
Purchase #4	$94.34	6.195%	$100.1844	$100.18	$100.20	$100.20
Purchase #5	$17.80	13.670%	$20.2333	$20.23	$20.25	$20.20
Purchase #6	$136.35	3.588%	$141.2422	$141.24	$141.25	$141.20
Purchase #7	$100.94	3.384%	$104.3558	$104.36	$104.35	$104.40
7 purchase totals =	$602.07		$646.7058	$646.69	$646.75	$646.70