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	$170.91	10.254%	$188.4351	$188.44	$188.45	$188.40
Purchase #2	$233.40	12.402%	$262.3463	$262.35	$262.35	$262.30
Purchase #3	$232.59	3.636%	$241.047	$241.05	$241.05	$241.00
Purchase #4	$131.38	7.726%	$141.5304	$141.53	$141.55	$141.50
Purchase #5	$125.58	11.406%	$139.9037	$139.90	$139.90	$139.90
Purchase #6	$93.48	6.205%	$99.2804	$99.28	$99.30	$99.30
Purchase #7	$164.28	4.485%	$171.648	$171.65	$171.65	$171.60
7 purchase totals =	$1,151.62		$1,244.1909	$1,244.20	$1,244.25	$1,244.00