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	$147.42	4.476%	$154.0185	$154.02	$154.00	$154.00
Purchase #2	$9.31	10.257%	$10.2649	$10.26	$10.25	$10.30
Purchase #3	$85.98	5.785%	$90.9539	$90.95	$90.95	$91.00
Purchase #4	$104.91	12.802%	$118.3406	$118.34	$118.35	$118.30
Purchase #5	$97.86	9.263%	$106.9248	$106.92	$106.90	$106.90
Purchase #6	$83.51	10.792%	$92.5224	$92.52	$92.50	$92.50
Purchase #7	$29.60	8.219%	$32.0328	$32.03	$32.05	$32.00
7 purchase totals =	$558.59		$605.0579	$605.04	$605.00	$605.00