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	$142.55	12.830%	$160.8392	$160.84	$160.85	$160.80
Purchase #2	$19.49	4.528%	$20.3725	$20.37	$20.35	$20.40
Purchase #3	$73.41	6.267%	$78.0106	$78.01	$78.00	$78.00
Purchase #4	$150.98	3.822%	$156.7505	$156.75	$156.75	$156.80
Purchase #5	$176.81	8.208%	$191.3226	$191.32	$191.30	$191.30
Purchase #6	$37.73	10.231%	$41.5902	$41.59	$41.60	$41.60
Purchase #7	$221.86	11.650%	$247.7067	$247.71	$247.70	$247.70
7 purchase totals =	$822.83		$896.5923	$896.59	$896.55	$896.60