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	$146.43	9.448%	$160.2647	$160.26	$160.25	$160.30
Purchase #2	$11.49	4.443%	$12.0005	$12.00	$12.00	$12.00
Purchase #3	$179.59	11.120%	$199.5604	$199.56	$199.55	$199.60
Purchase #4	$144.50	7.603%	$155.4863	$155.49	$155.50	$155.50
Purchase #5	$170.83	11.687%	$190.7949	$190.79	$190.80	$190.80
Purchase #6	$219.81	7.372%	$236.0144	$236.01	$236.00	$236.00
Purchase #7	$99.71	11.614%	$111.2903	$111.29	$111.30	$111.30
7 purchase totals =	$972.36		$1,065.4115	$1,065.40	$1,065.40	$1,065.50