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	$83.29	10.166%	$91.7573	$91.76	$91.75	$91.80
Purchase #2	$123.96	12.249%	$139.1439	$139.14	$139.15	$139.10
Purchase #3	$185.77	6.323%	$197.5162	$197.52	$197.50	$197.50
Purchase #4	$195.96	7.863%	$211.3683	$211.37	$211.35	$211.40
Purchase #5	$80.32	9.865%	$88.2436	$88.24	$88.25	$88.20
Purchase #6	$160.60	11.540%	$179.1332	$179.13	$179.15	$179.10
Purchase #7	$244.60	12.495%	$275.1628	$275.16	$275.15	$275.20
7 purchase totals =	$1,074.50		$1,182.3253	$1,182.32	$1,182.30	$1,182.30