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	$95.65	7.858%	$103.1662	$103.17	$103.15	$103.20
Purchase #2	$73.35	7.391%	$78.7713	$78.77	$78.75	$78.80
Purchase #3	$58.72	4.255%	$61.2185	$61.22	$61.20	$61.20
Purchase #4	$99.63	10.744%	$110.3342	$110.33	$110.35	$110.30
Purchase #5	$130.84	6.517%	$139.3668	$139.37	$139.35	$139.40
Purchase #6	$162.63	6.750%	$173.6075	$173.61	$173.60	$173.60
Purchase #7	$87.53	5.357%	$92.219	$92.22	$92.20	$92.20
7 purchase totals =	$708.35		$758.6835	$758.69	$758.60	$758.70