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	$123.81	5.707%	$130.8758	$130.88	$130.90	$130.90
Purchase #2	$56.49	5.416%	$59.5495	$59.55	$59.55	$59.50
Purchase #3	$72.80	7.227%	$78.0613	$78.06	$78.05	$78.10
Purchase #4	$190.92	7.489%	$205.218	$205.22	$205.20	$205.20
Purchase #5	$144.43	7.442%	$155.1785	$155.18	$155.20	$155.20
Purchase #6	$244.78	6.617%	$260.9771	$260.98	$261.00	$261.00
Purchase #7	$107.50	10.216%	$118.4822	$118.48	$118.50	$118.50
7 purchase totals =	$940.73		$1,008.3424	$1,008.35	$1,008.40	$1,008.40