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	$152.83	13.157%	$172.9378	$172.94	$172.95	$172.90
Purchase #2	$108.61	9.769%	$119.2201	$119.22	$119.20	$119.20
Purchase #3	$119.99	6.302%	$127.5518	$127.55	$127.55	$127.60
Purchase #4	$141.48	12.406%	$159.032	$159.03	$159.05	$159.00
Purchase #5	$54.94	12.155%	$61.618	$61.62	$61.60	$61.60
Purchase #6	$206.41	8.219%	$223.3748	$223.37	$223.35	$223.40
Purchase #7	$87.68	13.768%	$99.7518	$99.75	$99.75	$99.80
7 purchase totals =	$871.94		$963.4863	$963.48	$963.45	$963.50