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	$220.47	4.118%	$229.549	$229.55	$229.55	$229.50
Purchase #2	$206.52	11.376%	$230.0137	$230.01	$230.00	$230.00
Purchase #3	$96.76	4.630%	$101.24	$101.24	$101.25	$101.20
Purchase #4	$145.92	3.595%	$151.1658	$151.17	$151.15	$151.20
Purchase #5	$52.88	5.683%	$55.8852	$55.89	$55.90	$55.90
Purchase #6	$89.30	11.648%	$99.7017	$99.70	$99.70	$99.70
Purchase #7	$131.61	12.142%	$147.5901	$147.59	$147.60	$147.60
7 purchase totals =	$943.46		$1,015.1455	$1,015.15	$1,015.15	$1,015.10