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	$79.47	7.540%	$85.462	$85.46	$85.45	$85.50
Purchase #2	$199.52	10.213%	$219.897	$219.90	$219.90	$219.90
Purchase #3	$123.32	10.335%	$136.0651	$136.07	$136.05	$136.10
Purchase #4	$82.57	4.806%	$86.5383	$86.54	$86.55	$86.50
Purchase #5	$71.70	8.568%	$77.8433	$77.84	$77.85	$77.80
Purchase #6	$217.39	11.753%	$242.9398	$242.94	$242.95	$242.90
Purchase #7	$137.28	13.854%	$156.2988	$156.30	$156.30	$156.30
7 purchase totals =	$911.25		$1,005.0443	$1,005.05	$1,005.05	$1,005.00