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	$226.35	5.317%	$238.385	$238.39	$238.40	$238.40
Purchase #2	$45.45	8.861%	$49.4773	$49.48	$49.50	$49.50
Purchase #3	$249.56	9.721%	$273.8197	$273.82	$273.80	$273.80
Purchase #4	$64.71	9.750%	$71.0192	$71.02	$71.00	$71.00
Purchase #5	$65.68	10.193%	$72.3748	$72.37	$72.35	$72.40
Purchase #6	$238.47	4.719%	$249.7234	$249.72	$249.70	$249.70
Purchase #7	$213.27	7.451%	$229.1607	$229.16	$229.15	$229.20
7 purchase totals =	$1,103.49		$1,183.9601	$1,183.96	$1,183.90	$1,184.00