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	$57.89	7.536%	$62.2526	$62.25	$62.25	$62.30
Purchase #2	$149.76	6.597%	$159.6397	$159.64	$159.65	$159.60
Purchase #3	$120.28	6.279%	$127.8324	$127.83	$127.85	$127.80
Purchase #4	$220.96	13.122%	$249.9544	$249.95	$249.95	$250.00
Purchase #5	$133.46	8.324%	$144.5692	$144.57	$144.55	$144.60
Purchase #6	$76.55	7.872%	$82.576	$82.58	$82.60	$82.60
Purchase #7	$34.84	7.622%	$37.4955	$37.50	$37.50	$37.50
7 purchase totals =	$793.74		$864.3198	$864.32	$864.35	$864.40