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	$168.76	7.167%	$180.855	$180.86	$180.85	$180.90
Purchase #2	$150.96	9.581%	$165.4235	$165.42	$165.40	$165.40
Purchase #3	$156.75	7.260%	$168.1301	$168.13	$168.15	$168.10
Purchase #4	$77.32	9.698%	$84.8185	$84.82	$84.80	$84.80
Purchase #5	$11.67	6.105%	$12.3825	$12.38	$12.40	$12.40
Purchase #6	$230.86	11.278%	$256.8964	$256.90	$256.90	$256.90
Purchase #7	$154.53	3.489%	$159.9216	$159.92	$159.90	$159.90
7 purchase totals =	$950.85		$1,028.4276	$1,028.43	$1,028.40	$1,028.40