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	$10.39	7.186%	$11.1366	$11.14	$11.15	$11.10
Purchase #2	$199.91	5.313%	$210.5312	$210.53	$210.55	$210.50
Purchase #3	$63.56	11.644%	$70.9609	$70.96	$70.95	$71.00
Purchase #4	$215.70	8.696%	$234.4573	$234.46	$234.45	$234.50
Purchase #5	$237.70	8.676%	$258.3229	$258.32	$258.30	$258.30
Purchase #6	$193.31	10.422%	$213.4568	$213.46	$213.45	$213.50
Purchase #7	$77.78	5.779%	$82.2749	$82.27	$82.25	$82.30
7 purchase totals =	$998.35		$1,081.1406	$1,081.14	$1,081.10	$1,081.20