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	$69.88	9.709%	$76.6646	$76.66	$76.65	$76.70
Purchase #2	$70.31	12.121%	$78.8323	$78.83	$78.85	$78.80
Purchase #3	$164.98	6.396%	$175.5321	$175.53	$175.55	$175.50
Purchase #4	$139.55	4.230%	$145.453	$145.45	$145.45	$145.50
Purchase #5	$132.88	7.781%	$143.2194	$143.22	$143.20	$143.20
Purchase #6	$184.86	3.862%	$191.9993	$192.00	$192.00	$192.00
Purchase #7	$57.35	3.740%	$59.4949	$59.49	$59.50	$59.50
7 purchase totals =	$819.81		$871.1956	$871.18	$871.20	$871.20