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	$43.30	4.264%	$45.1463	$45.15	$45.15	$45.10
Purchase #2	$227.25	3.640%	$235.5219	$235.52	$235.50	$235.50
Purchase #3	$17.46	4.475%	$18.2413	$18.24	$18.25	$18.20
Purchase #4	$124.60	13.298%	$141.1693	$141.17	$141.15	$141.20
Purchase #5	$206.74	4.714%	$216.4857	$216.49	$216.50	$216.50
Purchase #6	$227.52	6.317%	$241.8924	$241.89	$241.90	$241.90
Purchase #7	$13.31	4.461%	$13.9038	$13.90	$13.90	$13.90
7 purchase totals =	$860.18		$912.3607	$912.36	$912.35	$912.30