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	$75.39	9.369%	$82.4533	$82.45	$82.45	$82.50
Purchase #2	$131.85	9.584%	$144.4865	$144.49	$144.50	$144.50
Purchase #3	$44.57	8.713%	$48.4534	$48.45	$48.45	$48.50
Purchase #4	$152.94	11.773%	$170.9456	$170.95	$170.95	$170.90
Purchase #5	$90.53	8.121%	$97.8819	$97.88	$97.90	$97.90
Purchase #6	$223.79	8.172%	$242.0781	$242.08	$242.10	$242.10
Purchase #7	$162.59	12.651%	$183.1593	$183.16	$183.15	$183.20
7 purchase totals =	$881.66		$969.4581	$969.46	$969.50	$969.60