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	$175.77	3.318%	$181.602	$181.60	$181.60	$181.60
Purchase #2	$197.77	11.424%	$220.3632	$220.36	$220.35	$220.40
Purchase #3	$122.77	4.433%	$128.2124	$128.21	$128.20	$128.20
Purchase #4	$35.78	5.496%	$37.7465	$37.75	$37.75	$37.70
Purchase #5	$74.56	12.113%	$83.5915	$83.59	$83.60	$83.60
Purchase #6	$46.88	12.190%	$52.5947	$52.59	$52.60	$52.60
Purchase #7	$36.50	5.743%	$38.5962	$38.60	$38.60	$38.60
7 purchase totals =	$690.03		$742.7065	$742.70	$742.70	$742.70