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	$206.98	6.531%	$220.4979	$220.50	$220.50	$220.50
Purchase #2	$99.38	4.175%	$103.5291	$103.53	$103.55	$103.50
Purchase #3	$89.76	5.533%	$94.7264	$94.73	$94.75	$94.70
Purchase #4	$248.89	13.208%	$281.7634	$281.76	$281.75	$281.80
Purchase #5	$198.63	6.805%	$212.1468	$212.15	$212.15	$212.10
Purchase #6	$221.90	10.196%	$244.5249	$244.52	$244.50	$244.50
Purchase #7	$131.58	6.233%	$139.7814	$139.78	$139.80	$139.80
7 purchase totals =	$1,197.12		$1,296.9699	$1,296.97	$1,297.00	$1,296.90