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	$196.56	13.111%	$222.331	$222.33	$222.35	$222.30
Purchase #2	$155.82	5.487%	$164.3698	$164.37	$164.35	$164.40
Purchase #3	$123.27	5.627%	$130.2064	$130.21	$130.20	$130.20
Purchase #4	$176.90	12.205%	$198.4906	$198.49	$198.50	$198.50
Purchase #5	$44.65	12.388%	$50.1812	$50.18	$50.20	$50.20
Purchase #6	$150.85	9.522%	$165.2139	$165.21	$165.20	$165.20
Purchase #7	$213.84	9.272%	$233.6672	$233.67	$233.65	$233.70
7 purchase totals =	$1,061.89		$1,164.4601	$1,164.46	$1,164.45	$1,164.50