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	$197.89	3.657%	$205.1268	$205.13	$205.15	$205.10
Purchase #2	$171.83	8.201%	$185.9218	$185.92	$185.90	$185.90
Purchase #3	$77.87	5.630%	$82.2541	$82.25	$82.25	$82.30
Purchase #4	$141.67	12.726%	$159.6989	$159.70	$159.70	$159.70
Purchase #5	$228.31	3.306%	$235.8579	$235.86	$235.85	$235.90
Purchase #6	$85.25	7.725%	$91.8356	$91.84	$91.85	$91.80
Purchase #7	$155.32	10.610%	$171.7995	$171.80	$171.80	$171.80
7 purchase totals =	$1,058.14		$1,132.4946	$1,132.50	$1,132.50	$1,132.50