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	$162.81	8.653%	$176.8979	$176.90	$176.90	$176.90
Purchase #2	$137.29	13.149%	$155.3423	$155.34	$155.35	$155.30
Purchase #3	$72.30	5.822%	$76.5093	$76.51	$76.50	$76.50
Purchase #4	$200.43	10.584%	$221.6435	$221.64	$221.65	$221.60
Purchase #5	$121.52	3.261%	$125.4828	$125.48	$125.50	$125.50
Purchase #6	$174.50	12.276%	$195.9216	$195.92	$195.90	$195.90
Purchase #7	$51.30	4.808%	$53.7665	$53.77	$53.75	$53.80
7 purchase totals =	$920.15		$1,005.5639	$1,005.56	$1,005.55	$1,005.50