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	$108.48	13.334%	$122.9447	$122.94	$122.95	$122.90
Purchase #2	$147.69	3.319%	$152.5918	$152.59	$152.60	$152.60
Purchase #3	$153.67	13.261%	$174.0482	$174.05	$174.05	$174.00
Purchase #4	$198.41	12.734%	$223.6755	$223.68	$223.70	$223.70
Purchase #5	$101.88	7.491%	$109.5118	$109.51	$109.50	$109.50
Purchase #6	$120.87	5.118%	$127.0561	$127.06	$127.05	$127.10
Purchase #7	$6.86	12.187%	$7.696	$7.70	$7.70	$7.70
7 purchase totals =	$837.86		$917.5241	$917.53	$917.55	$917.50