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	$216.54	6.140%	$229.8356	$229.84	$229.85	$229.80
Purchase #2	$42.30	12.795%	$47.7123	$47.71	$47.70	$47.70
Purchase #3	$8.29	7.834%	$8.9394	$8.94	$8.95	$8.90
Purchase #4	$68.29	6.350%	$72.6264	$72.63	$72.65	$72.60
Purchase #5	$99.41	11.699%	$111.04	$111.04	$111.05	$111.00
Purchase #6	$45.87	4.380%	$47.8791	$47.88	$47.90	$47.90
Purchase #7	$52.57	9.766%	$57.704	$57.70	$57.70	$57.70
7 purchase totals =	$533.27		$575.7368	$575.74	$575.80	$575.60