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	$165.60	11.312%	$184.3327	$184.33	$184.35	$184.30
Purchase #2	$197.56	13.290%	$223.8157	$223.82	$223.80	$223.80
Purchase #3	$40.85	4.847%	$42.83	$42.83	$42.85	$42.80
Purchase #4	$178.77	3.826%	$185.6097	$185.61	$185.60	$185.60
Purchase #5	$117.66	8.299%	$127.4246	$127.42	$127.40	$127.40
Purchase #6	$227.84	9.456%	$249.3846	$249.38	$249.40	$249.40
Purchase #7	$56.40	5.552%	$59.5313	$59.53	$59.55	$59.50
7 purchase totals =	$984.68		$1,072.9286	$1,072.92	$1,072.95	$1,072.80