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	$135.96	7.555%	$146.2318	$146.23	$146.25	$146.20
Purchase #2	$95.98	3.626%	$99.4602	$99.46	$99.45	$99.50
Purchase #3	$170.69	11.449%	$190.2323	$190.23	$190.25	$190.20
Purchase #4	$19.62	10.500%	$21.6801	$21.68	$21.70	$21.70
Purchase #5	$233.37	10.494%	$257.8598	$257.86	$257.85	$257.90
Purchase #6	$106.35	3.569%	$110.1456	$110.15	$110.15	$110.10
Purchase #7	$185.87	3.762%	$192.8624	$192.86	$192.85	$192.90
7 purchase totals =	$947.84		$1,018.4722	$1,018.47	$1,018.50	$1,018.50