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	$183.25	11.549%	$204.4135	$204.41	$204.40	$204.40
Purchase #2	$138.61	4.520%	$144.8752	$144.88	$144.90	$144.90
Purchase #3	$145.90	4.791%	$152.8901	$152.89	$152.90	$152.90
Purchase #4	$47.58	5.369%	$50.1346	$50.13	$50.15	$50.10
Purchase #5	$53.76	9.836%	$59.0478	$59.05	$59.05	$59.00
Purchase #6	$216.89	4.437%	$226.5134	$226.51	$226.50	$226.50
Purchase #7	$14.26	6.431%	$15.1771	$15.18	$15.20	$15.20
7 purchase totals =	$800.25		$853.0517	$853.05	$853.10	$853.00