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	$114.59	13.451%	$130.0035	$130.00	$130.00	$130.00
Purchase #2	$203.44	10.398%	$224.5937	$224.59	$224.60	$224.60
Purchase #3	$202.78	4.706%	$212.3228	$212.32	$212.30	$212.30
Purchase #4	$35.30	8.873%	$38.4322	$38.43	$38.45	$38.40
Purchase #5	$156.27	3.259%	$161.3628	$161.36	$161.35	$161.40
Purchase #6	$106.44	4.864%	$111.6172	$111.62	$111.60	$111.60
Purchase #7	$102.89	8.284%	$111.4134	$111.41	$111.40	$111.40
7 purchase totals =	$921.71		$989.7456	$989.73	$989.70	$989.70