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	$129.27	6.330%	$137.4528	$137.45	$137.45	$137.50
Purchase #2	$174.61	10.432%	$192.8253	$192.83	$192.85	$192.80
Purchase #3	$206.82	5.190%	$217.554	$217.55	$217.55	$217.60
Purchase #4	$85.27	7.285%	$91.4819	$91.48	$91.50	$91.50
Purchase #5	$134.37	12.857%	$151.646	$151.65	$151.65	$151.60
Purchase #6	$117.79	7.847%	$127.033	$127.03	$127.05	$127.00
Purchase #7	$137.65	3.406%	$142.3384	$142.34	$142.35	$142.30
7 purchase totals =	$985.78		$1,060.3314	$1,060.33	$1,060.40	$1,060.30