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	$30.39	9.603%	$33.3084	$33.31	$33.30	$33.30
Purchase #2	$177.32	4.475%	$185.2551	$185.26	$185.25	$185.30
Purchase #3	$216.53	11.828%	$242.1412	$242.14	$242.15	$242.10
Purchase #4	$21.76	5.493%	$22.9553	$22.96	$22.95	$23.00
Purchase #5	$183.64	4.149%	$191.2592	$191.26	$191.25	$191.30
Purchase #6	$130.86	10.126%	$144.1109	$144.11	$144.10	$144.10
Purchase #7	$174.29	11.636%	$194.5704	$194.57	$194.55	$194.60
7 purchase totals =	$934.79		$1,013.6005	$1,013.61	$1,013.55	$1,013.70