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	$182.46	7.611%	$196.347	$196.35	$196.35	$196.30
Purchase #2	$92.93	13.624%	$105.5908	$105.59	$105.60	$105.60
Purchase #3	$99.44	5.366%	$104.776	$104.78	$104.80	$104.80
Purchase #4	$76.88	8.540%	$83.4456	$83.45	$83.45	$83.40
Purchase #5	$72.47	4.265%	$75.5608	$75.56	$75.55	$75.60
Purchase #6	$20.98	4.335%	$21.8895	$21.89	$21.90	$21.90
Purchase #7	$142.49	7.482%	$153.1511	$153.15	$153.15	$153.20
7 purchase totals =	$687.65		$740.7608	$740.77	$740.80	$740.80