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	$99.85	4.651%	$104.494	$104.49	$104.50	$104.50
Purchase #2	$70.27	11.804%	$78.5647	$78.56	$78.55	$78.60
Purchase #3	$155.92	6.863%	$166.6208	$166.62	$166.60	$166.60
Purchase #4	$89.53	13.546%	$101.6577	$101.66	$101.65	$101.70
Purchase #5	$150.41	9.788%	$165.1321	$165.13	$165.15	$165.10
Purchase #6	$247.60	12.816%	$279.3324	$279.33	$279.35	$279.30
Purchase #7	$211.73	9.214%	$231.2388	$231.24	$231.25	$231.20
7 purchase totals =	$1,025.31		$1,127.0405	$1,127.03	$1,127.05	$1,127.00