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	$219.31	8.736%	$238.4689	$238.47	$238.45	$238.50
Purchase #2	$37.71	6.786%	$40.269	$40.27	$40.25	$40.30
Purchase #3	$38.62	6.423%	$41.1006	$41.10	$41.10	$41.10
Purchase #4	$175.80	3.733%	$182.3626	$182.36	$182.35	$182.40
Purchase #5	$33.49	3.659%	$34.7154	$34.72	$34.70	$34.70
Purchase #6	$81.57	13.822%	$92.8446	$92.84	$92.85	$92.80
Purchase #7	$127.74	11.838%	$142.8619	$142.86	$142.85	$142.90
7 purchase totals =	$714.24		$772.6230	$772.62	$772.55	$772.70