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	$232.31	8.337%	$251.6777	$251.68	$251.70	$251.70
Purchase #2	$176.47	9.300%	$192.8817	$192.88	$192.90	$192.90
Purchase #3	$37.36	7.412%	$40.1291	$40.13	$40.15	$40.10
Purchase #4	$191.29	9.443%	$209.3535	$209.35	$209.35	$209.40
Purchase #5	$211.39	4.699%	$221.3232	$221.32	$221.30	$221.30
Purchase #6	$68.94	7.140%	$73.8623	$73.86	$73.85	$73.90
Purchase #7	$29.80	10.336%	$32.8801	$32.88	$32.90	$32.90
7 purchase totals =	$947.56		$1,022.1076	$1,022.10	$1,022.15	$1,022.20