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	$204.87	3.761%	$212.5752	$212.58	$212.60	$212.60
Purchase #2	$25.79	9.362%	$28.2045	$28.20	$28.20	$28.20
Purchase #3	$36.34	4.189%	$37.8623	$37.86	$37.85	$37.90
Purchase #4	$72.63	11.245%	$80.7972	$80.80	$80.80	$80.80
Purchase #5	$245.67	13.597%	$279.0737	$279.07	$279.05	$279.10
Purchase #6	$175.79	5.859%	$186.0895	$186.09	$186.10	$186.10
Purchase #7	$247.33	3.468%	$255.9074	$255.91	$255.90	$255.90
7 purchase totals =	$1,008.42		$1,080.5098	$1,080.51	$1,080.50	$1,080.60