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	$81.79	8.709%	$88.9131	$88.91	$88.90	$88.90
Purchase #2	$69.36	13.216%	$78.5266	$78.53	$78.55	$78.50
Purchase #3	$105.52	11.146%	$117.2813	$117.28	$117.30	$117.30
Purchase #4	$188.49	4.389%	$196.7628	$196.76	$196.75	$196.80
Purchase #5	$84.60	4.372%	$88.2987	$88.30	$88.30	$88.30
Purchase #6	$72.47	11.381%	$80.7178	$80.72	$80.70	$80.70
Purchase #7	$153.89	4.626%	$161.009	$161.01	$161.00	$161.00
7 purchase totals =	$756.12		$811.5093	$811.51	$811.50	$811.50