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	$244.67	13.156%	$276.8588	$276.86	$276.85	$276.90
Purchase #2	$236.57	3.721%	$245.3728	$245.37	$245.35	$245.40
Purchase #3	$16.32	9.167%	$17.8161	$17.82	$17.80	$17.80
Purchase #4	$50.77	10.864%	$56.2857	$56.29	$56.30	$56.30
Purchase #5	$32.45	9.204%	$35.4367	$35.44	$35.45	$35.40
Purchase #6	$244.72	12.499%	$275.3076	$275.31	$275.30	$275.30
Purchase #7	$244.59	4.295%	$255.0951	$255.10	$255.10	$255.10
7 purchase totals =	$1,070.09		$1,162.1728	$1,162.19	$1,162.15	$1,162.20