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	$181.82	10.692%	$201.2602	$201.26	$201.25	$201.30
Purchase #2	$30.95	3.417%	$32.0076	$32.01	$32.00	$32.00
Purchase #3	$136.40	5.692%	$144.1639	$144.16	$144.15	$144.20
Purchase #4	$43.93	6.497%	$46.7841	$46.78	$46.80	$46.80
Purchase #5	$78.86	5.855%	$83.4773	$83.48	$83.50	$83.50
Purchase #6	$45.26	13.740%	$51.4787	$51.48	$51.50	$51.50
Purchase #7	$196.90	13.656%	$223.7887	$223.79	$223.80	$223.80
7 purchase totals =	$714.12		$782.9605	$782.96	$783.00	$783.10