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	$236.60	7.866%	$255.211	$255.21	$255.20	$255.20
Purchase #2	$54.36	9.114%	$59.3144	$59.31	$59.30	$59.30
Purchase #3	$244.45	7.221%	$262.1017	$262.10	$262.10	$262.10
Purchase #4	$69.65	3.479%	$72.0731	$72.07	$72.05	$72.10
Purchase #5	$82.30	4.591%	$86.0784	$86.08	$86.10	$86.10
Purchase #6	$204.36	8.590%	$221.9145	$221.91	$221.90	$221.90
Purchase #7	$150.25	6.680%	$160.2867	$160.29	$160.30	$160.30
7 purchase totals =	$1,041.97		$1,116.9798	$1,116.97	$1,116.95	$1,117.00