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	$93.37	11.274%	$103.8965	$103.90	$103.90	$103.90
Purchase #2	$214.63	8.758%	$233.4273	$233.43	$233.45	$233.40
Purchase #3	$48.46	5.604%	$51.1757	$51.18	$51.20	$51.20
Purchase #4	$184.92	12.501%	$208.0368	$208.04	$208.05	$208.00
Purchase #5	$44.96	13.231%	$50.9087	$50.91	$50.90	$50.90
Purchase #6	$73.92	12.310%	$83.0196	$83.02	$83.00	$83.00
Purchase #7	$66.90	6.134%	$71.0036	$71.00	$71.00	$71.00
7 purchase totals =	$727.16		$801.4682	$801.48	$801.50	$801.40