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	$42.99	9.234%	$46.9597	$46.96	$46.95	$47.00
Purchase #2	$171.93	6.182%	$182.5587	$182.56	$182.55	$182.60
Purchase #3	$102.57	8.584%	$111.3746	$111.37	$111.35	$111.40
Purchase #4	$236.34	4.772%	$247.6181	$247.62	$247.60	$247.60
Purchase #5	$133.40	8.579%	$144.8444	$144.84	$144.85	$144.80
Purchase #6	$95.92	9.868%	$105.3854	$105.39	$105.40	$105.40
Purchase #7	$41.42	9.338%	$45.2878	$45.29	$45.30	$45.30
7 purchase totals =	$824.57		$884.0287	$884.03	$884.00	$884.10