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	$183.75	3.528%	$190.2327	$190.23	$190.25	$190.20
Purchase #2	$43.80	3.733%	$45.4351	$45.44	$45.45	$45.40
Purchase #3	$24.39	3.144%	$25.1568	$25.16	$25.15	$25.20
Purchase #4	$80.28	13.139%	$90.828	$90.83	$90.85	$90.80
Purchase #5	$139.40	4.111%	$145.1307	$145.13	$145.15	$145.10
Purchase #6	$233.77	10.438%	$258.1709	$258.17	$258.15	$258.20
Purchase #7	$94.46	3.545%	$97.8086	$97.81	$97.80	$97.80
7 purchase totals =	$799.85		$852.7628	$852.77	$852.80	$852.70