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	$102.57	9.621%	$112.4383	$112.44	$112.45	$112.40
Purchase #2	$214.75	12.735%	$242.0984	$242.10	$242.10	$242.10
Purchase #3	$93.41	9.855%	$102.6156	$102.62	$102.60	$102.60
Purchase #4	$204.46	8.577%	$221.9965	$222.00	$222.00	$222.00
Purchase #5	$95.64	5.487%	$100.8878	$100.89	$100.90	$100.90
Purchase #6	$73.60	12.530%	$82.8221	$82.82	$82.80	$82.80
Purchase #7	$153.32	4.232%	$159.8085	$159.81	$159.80	$159.80
7 purchase totals =	$937.75		$1,022.6672	$1,022.68	$1,022.65	$1,022.60