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	$113.47	12.103%	$127.2033	$127.20	$127.20	$127.20
Purchase #2	$42.28	3.714%	$43.8503	$43.85	$43.85	$43.90
Purchase #3	$238.87	7.831%	$257.5759	$257.58	$257.60	$257.60
Purchase #4	$216.44	8.209%	$234.2076	$234.21	$234.20	$234.20
Purchase #5	$140.42	13.125%	$158.8501	$158.85	$158.85	$158.90
Purchase #6	$142.76	3.171%	$147.2869	$147.29	$147.30	$147.30
Purchase #7	$51.71	5.128%	$54.3617	$54.36	$54.35	$54.40
7 purchase totals =	$945.95		$1,023.3358	$1,023.34	$1,023.35	$1,023.50