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	$93.87	12.836%	$105.9192	$105.92	$105.90	$105.90
Purchase #2	$81.43	11.594%	$90.871	$90.87	$90.85	$90.90
Purchase #3	$102.57	8.780%	$111.5756	$111.58	$111.60	$111.60
Purchase #4	$26.91	4.550%	$28.1344	$28.13	$28.15	$28.10
Purchase #5	$206.32	6.766%	$220.2796	$220.28	$220.30	$220.30
Purchase #6	$209.81	12.565%	$236.1726	$236.17	$236.15	$236.20
Purchase #7	$246.85	11.647%	$275.6006	$275.60	$275.60	$275.60
7 purchase totals =	$967.76		$1,068.5530	$1,068.55	$1,068.55	$1,068.60