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	$195.55	13.667%	$222.2758	$222.28	$222.30	$222.30
Purchase #2	$10.78	6.792%	$11.5122	$11.51	$11.50	$11.50
Purchase #3	$199.91	11.462%	$222.8237	$222.82	$222.80	$222.80
Purchase #4	$89.29	4.318%	$93.1455	$93.15	$93.15	$93.10
Purchase #5	$245.51	6.678%	$261.9052	$261.91	$261.90	$261.90
Purchase #6	$12.61	12.466%	$14.182	$14.18	$14.20	$14.20
Purchase #7	$247.60	10.796%	$274.3309	$274.33	$274.35	$274.30
7 purchase totals =	$1,001.25		$1,100.1753	$1,100.18	$1,100.20	$1,100.10