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	$171.71	12.396%	$192.9952	$193.00	$193.00	$193.00
Purchase #2	$211.74	10.189%	$233.3142	$233.31	$233.30	$233.30
Purchase #3	$78.86	6.312%	$83.8376	$83.84	$83.85	$83.80
Purchase #4	$172.61	7.234%	$185.0966	$185.10	$185.10	$185.10
Purchase #5	$73.34	13.581%	$83.3003	$83.30	$83.30	$83.30
Purchase #6	$40.34	8.859%	$43.9137	$43.91	$43.90	$43.90
Purchase #7	$211.82	9.803%	$232.5847	$232.58	$232.60	$232.60
7 purchase totals =	$960.42		$1,055.0423	$1,055.04	$1,055.05	$1,055.00