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	$131.51	10.209%	$144.9359	$144.94	$144.95	$144.90
Purchase #2	$248.25	6.497%	$264.3788	$264.38	$264.40	$264.40
Purchase #3	$249.46	13.114%	$282.1742	$282.17	$282.15	$282.20
Purchase #4	$143.80	6.285%	$152.8378	$152.84	$152.85	$152.80
Purchase #5	$152.87	5.323%	$161.0073	$161.01	$161.00	$161.00
Purchase #6	$113.80	12.114%	$127.5857	$127.59	$127.60	$127.60
Purchase #7	$13.47	4.742%	$14.1087	$14.11	$14.10	$14.10
7 purchase totals =	$1,053.16		$1,147.0284	$1,147.04	$1,147.05	$1,147.00