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	$86.25	3.824%	$89.5482	$89.55	$89.55	$89.50
Purchase #2	$44.78	8.698%	$48.675	$48.68	$48.70	$48.70
Purchase #3	$96.65	12.802%	$109.0231	$109.02	$109.00	$109.00
Purchase #4	$61.28	8.709%	$66.6169	$66.62	$66.60	$66.60
Purchase #5	$46.70	12.654%	$52.6094	$52.61	$52.60	$52.60
Purchase #6	$76.34	3.660%	$79.134	$79.13	$79.15	$79.10
Purchase #7	$91.79	12.245%	$103.0297	$103.03	$103.05	$103.00
7 purchase totals =	$503.79		$548.6363	$548.64	$548.65	$548.50