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	$200.56	13.368%	$227.3709	$227.37	$227.35	$227.40
Purchase #2	$50.26	11.108%	$55.8429	$55.84	$55.85	$55.80
Purchase #3	$62.95	12.296%	$70.6903	$70.69	$70.70	$70.70
Purchase #4	$24.59	13.267%	$27.8524	$27.85	$27.85	$27.90
Purchase #5	$19.88	13.635%	$22.5906	$22.59	$22.60	$22.60
Purchase #6	$74.33	10.850%	$82.3948	$82.39	$82.40	$82.40
Purchase #7	$69.52	10.265%	$76.6562	$76.66	$76.65	$76.70
7 purchase totals =	$502.09		$563.3981	$563.39	$563.40	$563.50