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	$111.84	10.822%	$123.9433	$123.94	$123.95	$123.90
Purchase #2	$68.81	5.727%	$72.7507	$72.75	$72.75	$72.80
Purchase #3	$34.87	7.688%	$37.5508	$37.55	$37.55	$37.60
Purchase #4	$81.95	6.697%	$87.4382	$87.44	$87.45	$87.40
Purchase #5	$218.48	10.510%	$241.4422	$241.44	$241.45	$241.40
Purchase #6	$241.72	9.799%	$265.4061	$265.41	$265.40	$265.40
Purchase #7	$35.89	9.469%	$39.2884	$39.29	$39.30	$39.30
7 purchase totals =	$793.56		$867.8197	$867.82	$867.85	$867.80