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	$148.33	11.343%	$165.1551	$165.16	$165.15	$165.20
Purchase #2	$96.78	11.462%	$107.8729	$107.87	$107.85	$107.90
Purchase #3	$126.99	10.502%	$140.3265	$140.33	$140.35	$140.30
Purchase #4	$133.41	11.580%	$148.8589	$148.86	$148.85	$148.90
Purchase #5	$218.29	6.766%	$233.0595	$233.06	$233.05	$233.10
Purchase #6	$32.39	9.205%	$35.3715	$35.37	$35.35	$35.40
Purchase #7	$205.91	6.269%	$218.8185	$218.82	$218.80	$218.80
7 purchase totals =	$962.10		$1,049.4629	$1,049.47	$1,049.40	$1,049.60