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	$192.90	6.694%	$205.8127	$205.81	$205.80	$205.80
Purchase #2	$187.89	3.313%	$194.1148	$194.11	$194.10	$194.10
Purchase #3	$151.78	8.685%	$164.9621	$164.96	$164.95	$165.00
Purchase #4	$234.71	10.761%	$259.9671	$259.97	$259.95	$260.00
Purchase #5	$172.57	3.405%	$178.446	$178.45	$178.45	$178.40
Purchase #6	$105.66	5.782%	$111.7693	$111.77	$111.75	$111.80
Purchase #7	$129.40	9.144%	$141.2323	$141.23	$141.25	$141.20
7 purchase totals =	$1,174.91		$1,256.3043	$1,256.30	$1,256.25	$1,256.30