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	$40.59	9.734%	$44.541	$44.54	$44.55	$44.50
Purchase #2	$49.54	8.703%	$53.8515	$53.85	$53.85	$53.90
Purchase #3	$197.81	7.368%	$212.3846	$212.38	$212.40	$212.40
Purchase #4	$169.62	11.340%	$188.8549	$188.85	$188.85	$188.90
Purchase #5	$217.77	9.660%	$238.8066	$238.81	$238.80	$238.80
Purchase #6	$148.49	10.769%	$164.4809	$164.48	$164.50	$164.50
Purchase #7	$79.72	12.151%	$89.4068	$89.41	$89.40	$89.40
7 purchase totals =	$903.54		$992.3263	$992.32	$992.35	$992.40