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	$36.86	9.780%	$40.4649	$40.46	$40.45	$40.50
Purchase #2	$10.33	7.412%	$11.0957	$11.10	$11.10	$11.10
Purchase #3	$177.55	5.804%	$187.855	$187.86	$187.85	$187.90
Purchase #4	$234.92	13.357%	$266.2983	$266.30	$266.30	$266.30
Purchase #5	$127.79	6.530%	$136.1347	$136.13	$136.15	$136.10
Purchase #6	$129.25	13.557%	$146.7724	$146.77	$146.75	$146.80
Purchase #7	$231.33	13.761%	$263.1633	$263.16	$263.15	$263.20
7 purchase totals =	$948.03		$1,051.7843	$1,051.78	$1,051.75	$1,051.90