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	$136.63	11.131%	$151.8383	$151.84	$151.85	$151.80
Purchase #2	$230.93	11.576%	$257.6625	$257.66	$257.65	$257.70
Purchase #3	$173.28	8.763%	$188.4645	$188.46	$188.45	$188.50
Purchase #4	$120.48	5.853%	$127.5317	$127.53	$127.55	$127.50
Purchase #5	$179.39	4.690%	$187.8034	$187.80	$187.80	$187.80
Purchase #6	$81.41	5.245%	$85.68	$85.68	$85.70	$85.70
Purchase #7	$100.61	10.187%	$110.8591	$110.86	$110.85	$110.90
7 purchase totals =	$1,022.73		$1,109.8395	$1,109.83	$1,109.85	$1,109.90