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	$127.82	7.266%	$137.1074	$137.11	$137.10	$137.10
Purchase #2	$35.56	5.680%	$37.5798	$37.58	$37.60	$37.60
Purchase #3	$75.30	13.145%	$85.1982	$85.20	$85.20	$85.20
Purchase #4	$39.89	10.584%	$44.112	$44.11	$44.10	$44.10
Purchase #5	$112.60	5.375%	$118.6523	$118.65	$118.65	$118.70
Purchase #6	$56.75	13.561%	$64.4459	$64.45	$64.45	$64.40
Purchase #7	$161.51	10.479%	$178.4346	$178.43	$178.45	$178.40
7 purchase totals =	$609.43		$665.5302	$665.53	$665.55	$665.50