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	$132.77	7.653%	$142.9309	$142.93	$142.95	$142.90
Purchase #2	$242.54	3.544%	$251.1356	$251.14	$251.15	$251.10
Purchase #3	$29.70	10.778%	$32.9011	$32.90	$32.90	$32.90
Purchase #4	$90.77	12.132%	$101.7822	$101.78	$101.80	$101.80
Purchase #5	$45.52	12.535%	$51.2259	$51.23	$51.25	$51.20
Purchase #6	$191.80	3.822%	$199.1306	$199.13	$199.15	$199.10
Purchase #7	$43.43	11.609%	$48.4718	$48.47	$48.45	$48.50
7 purchase totals =	$776.53		$827.5781	$827.58	$827.65	$827.50