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	$83.94	6.413%	$89.3231	$89.32	$89.30	$89.30
Purchase #2	$102.86	10.492%	$113.6521	$113.65	$113.65	$113.70
Purchase #3	$143.57	10.465%	$158.5946	$158.59	$158.60	$158.60
Purchase #4	$70.37	6.626%	$75.0327	$75.03	$75.05	$75.00
Purchase #5	$108.96	13.293%	$123.4441	$123.44	$123.45	$123.40
Purchase #6	$145.72	11.497%	$162.4734	$162.47	$162.45	$162.50
Purchase #7	$213.80	7.649%	$230.1536	$230.15	$230.15	$230.20
7 purchase totals =	$869.22		$952.6736	$952.65	$952.65	$952.70