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	$71.53	9.393%	$78.2488	$78.25	$78.25	$78.20
Purchase #2	$81.27	8.332%	$88.0414	$88.04	$88.05	$88.00
Purchase #3	$33.83	9.809%	$37.1484	$37.15	$37.15	$37.10
Purchase #4	$9.86	3.698%	$10.2246	$10.22	$10.20	$10.20
Purchase #5	$88.40	12.874%	$99.7806	$99.78	$99.80	$99.80
Purchase #6	$67.63	11.149%	$75.1701	$75.17	$75.15	$75.20
Purchase #7	$142.29	8.871%	$154.9125	$154.91	$154.90	$154.90
7 purchase totals =	$494.81		$543.5264	$543.52	$543.50	$543.40