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	$103.60	8.650%	$112.5614	$112.56	$112.55	$112.60
Purchase #2	$243.46	6.415%	$259.078	$259.08	$259.10	$259.10
Purchase #3	$78.27	11.341%	$87.1466	$87.15	$87.15	$87.10
Purchase #4	$36.25	7.380%	$38.9253	$38.93	$38.95	$38.90
Purchase #5	$6.83	10.153%	$7.5234	$7.52	$7.50	$7.50
Purchase #6	$225.68	7.447%	$242.4864	$242.49	$242.50	$242.50
Purchase #7	$178.85	6.864%	$191.1263	$191.13	$191.15	$191.10
7 purchase totals =	$872.94		$938.8474	$938.86	$938.90	$938.80