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	$153.72	7.243%	$164.8539	$164.85	$164.85	$164.90
Purchase #2	$160.85	13.250%	$182.1626	$182.16	$182.15	$182.20
Purchase #3	$143.67	11.185%	$159.7395	$159.74	$159.75	$159.70
Purchase #4	$119.54	8.137%	$129.267	$129.27	$129.25	$129.30
Purchase #5	$204.72	11.512%	$228.2874	$228.29	$228.30	$228.30
Purchase #6	$185.85	13.412%	$210.7762	$210.78	$210.80	$210.80
Purchase #7	$6.72	4.709%	$7.0364	$7.04	$7.05	$7.00
7 purchase totals =	$975.07		$1,082.1230	$1,082.13	$1,082.15	$1,082.20