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	$129.81	12.580%	$146.1401	$146.14	$146.15	$146.10
Purchase #2	$16.43	6.643%	$17.5214	$17.52	$17.50	$17.50
Purchase #3	$142.70	9.429%	$156.1552	$156.16	$156.15	$156.20
Purchase #4	$43.61	3.748%	$45.2445	$45.24	$45.25	$45.20
Purchase #5	$160.36	13.360%	$181.7841	$181.78	$181.80	$181.80
Purchase #6	$215.42	8.606%	$233.959	$233.96	$233.95	$234.00
Purchase #7	$200.63	10.862%	$222.4224	$222.42	$222.40	$222.40
7 purchase totals =	$908.96		$1,003.2267	$1,003.22	$1,003.20	$1,003.20