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	$237.29	12.320%	$266.5241	$266.52	$266.50	$266.50
Purchase #2	$180.29	6.433%	$191.8881	$191.89	$191.90	$191.90
Purchase #3	$245.73	4.431%	$256.6183	$256.62	$256.60	$256.60
Purchase #4	$186.58	5.428%	$196.7076	$196.71	$196.70	$196.70
Purchase #5	$227.79	5.262%	$239.7763	$239.78	$239.80	$239.80
Purchase #6	$235.67	12.304%	$264.6668	$264.67	$264.65	$264.70
Purchase #7	$170.95	8.435%	$185.3696	$185.37	$185.35	$185.40
7 purchase totals =	$1,484.30		$1,601.5508	$1,601.56	$1,601.50	$1,601.60