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	$205.27	13.324%	$232.6202	$232.62	$232.60	$232.60
Purchase #2	$212.70	10.299%	$234.606	$234.61	$234.60	$234.60
Purchase #3	$183.78	13.394%	$208.3955	$208.40	$208.40	$208.40
Purchase #4	$46.57	13.210%	$52.7219	$52.72	$52.70	$52.70
Purchase #5	$159.79	12.498%	$179.7606	$179.76	$179.75	$179.80
Purchase #6	$127.89	4.854%	$134.0978	$134.10	$134.10	$134.10
Purchase #7	$38.52	9.300%	$42.1024	$42.10	$42.10	$42.10
7 purchase totals =	$974.52		$1,084.3044	$1,084.31	$1,084.25	$1,084.30