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	$40.92	5.707%	$43.2553	$43.26	$43.25	$43.30
Purchase #2	$143.35	6.343%	$152.4427	$152.44	$152.45	$152.40
Purchase #3	$208.42	6.445%	$221.8527	$221.85	$221.85	$221.90
Purchase #4	$77.81	3.351%	$80.4174	$80.42	$80.40	$80.40
Purchase #5	$35.80	3.864%	$37.1833	$37.18	$37.20	$37.20
Purchase #6	$224.89	11.201%	$250.0799	$250.08	$250.10	$250.10
Purchase #7	$110.72	7.790%	$119.3451	$119.35	$119.35	$119.30
7 purchase totals =	$841.91		$904.5764	$904.58	$904.60	$904.60