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	$177.95	3.871%	$184.8384	$184.84	$184.85	$184.80
Purchase #2	$39.63	5.742%	$41.9056	$41.91	$41.90	$41.90
Purchase #3	$123.82	6.140%	$131.4225	$131.42	$131.40	$131.40
Purchase #4	$88.45	8.380%	$95.8621	$95.86	$95.85	$95.90
Purchase #5	$79.58	11.683%	$88.8773	$88.88	$88.90	$88.90
Purchase #6	$41.27	12.721%	$46.52	$46.52	$46.50	$46.50
Purchase #7	$65.88	11.194%	$73.2546	$73.25	$73.25	$73.30
7 purchase totals =	$616.58		$662.6805	$662.68	$662.65	$662.70