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	$151.95	9.479%	$166.3533	$166.35	$166.35	$166.40
Purchase #2	$141.36	6.472%	$150.5088	$150.51	$150.50	$150.50
Purchase #3	$67.25	11.730%	$75.1384	$75.14	$75.15	$75.10
Purchase #4	$161.52	3.754%	$167.5835	$167.58	$167.60	$167.60
Purchase #5	$186.46	5.181%	$196.1205	$196.12	$196.10	$196.10
Purchase #6	$213.27	12.752%	$240.4662	$240.47	$240.45	$240.50
Purchase #7	$138.34	9.764%	$151.8475	$151.85	$151.85	$151.80
7 purchase totals =	$1,060.15		$1,148.0182	$1,148.02	$1,148.00	$1,148.00