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	$241.47	9.571%	$264.5811	$264.58	$264.60	$264.60
Purchase #2	$38.85	10.706%	$43.0093	$43.01	$43.00	$43.00
Purchase #3	$83.54	9.499%	$91.4755	$91.48	$91.50	$91.50
Purchase #4	$63.87	7.240%	$68.4942	$68.49	$68.50	$68.50
Purchase #5	$131.82	10.502%	$145.6637	$145.66	$145.65	$145.70
Purchase #6	$59.39	8.646%	$64.5249	$64.52	$64.50	$64.50
Purchase #7	$27.34	7.130%	$29.2893	$29.29	$29.30	$29.30
7 purchase totals =	$646.28		$707.0380	$707.03	$707.05	$707.10