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	$96.72	7.190%	$103.6742	$103.67	$103.65	$103.70
Purchase #2	$91.68	13.163%	$103.7478	$103.75	$103.75	$103.70
Purchase #3	$10.79	5.822%	$11.4182	$11.42	$11.40	$11.40
Purchase #4	$200.87	5.731%	$212.3819	$212.38	$212.40	$212.40
Purchase #5	$82.90	7.577%	$89.1813	$89.18	$89.20	$89.20
Purchase #6	$86.79	6.334%	$92.2873	$92.29	$92.30	$92.30
Purchase #7	$110.29	12.602%	$124.1887	$124.19	$124.20	$124.20
7 purchase totals =	$680.04		$736.8794	$736.88	$736.90	$736.90