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	$147.89	3.842%	$153.5719	$153.57	$153.55	$153.60
Purchase #2	$32.68	12.517%	$36.7706	$36.77	$36.75	$36.80
Purchase #3	$119.54	6.402%	$127.193	$127.19	$127.20	$127.20
Purchase #4	$29.50	13.592%	$33.5096	$33.51	$33.50	$33.50
Purchase #5	$216.99	5.309%	$228.51	$228.51	$228.50	$228.50
Purchase #6	$237.61	10.413%	$262.3523	$262.35	$262.35	$262.40
Purchase #7	$7.27	4.685%	$7.6106	$7.61	$7.60	$7.60
7 purchase totals =	$791.48		$849.5180	$849.51	$849.45	$849.60