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	$102.71	8.481%	$111.4208	$111.42	$111.40	$111.40
Purchase #2	$175.64	5.799%	$185.8254	$185.83	$185.85	$185.80
Purchase #3	$126.67	11.590%	$141.3511	$141.35	$141.35	$141.40
Purchase #4	$114.52	6.167%	$121.5824	$121.58	$121.60	$121.60
Purchase #5	$122.40	6.441%	$130.2838	$130.28	$130.30	$130.30
Purchase #6	$250.96	12.389%	$282.0514	$282.05	$282.05	$282.10
Purchase #7	$188.88	9.867%	$207.5168	$207.52	$207.50	$207.50
7 purchase totals =	$1,081.78		$1,180.0317	$1,180.03	$1,180.05	$1,180.10