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	$114.44	11.395%	$127.4804	$127.48	$127.50	$127.50
Purchase #2	$66.96	7.603%	$72.051	$72.05	$72.05	$72.10
Purchase #3	$25.27	11.513%	$28.1793	$28.18	$28.20	$28.20
Purchase #4	$128.32	10.540%	$141.8449	$141.84	$141.85	$141.80
Purchase #5	$43.49	10.451%	$48.0351	$48.04	$48.05	$48.00
Purchase #6	$90.35	8.279%	$97.8301	$97.83	$97.85	$97.80
Purchase #7	$82.32	12.273%	$92.4231	$92.42	$92.40	$92.40
7 purchase totals =	$551.15		$607.8439	$607.84	$607.90	$607.80