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	$198.99	4.243%	$207.4331	$207.43	$207.45	$207.40
Purchase #2	$189.89	13.739%	$215.979	$215.98	$216.00	$216.00
Purchase #3	$116.31	9.334%	$127.1664	$127.17	$127.15	$127.20
Purchase #4	$197.81	4.227%	$206.1714	$206.17	$206.15	$206.20
Purchase #5	$59.43	10.561%	$65.7064	$65.71	$65.70	$65.70
Purchase #6	$68.78	13.408%	$78.002	$78.00	$78.00	$78.00
Purchase #7	$156.68	5.191%	$164.8133	$164.81	$164.80	$164.80
7 purchase totals =	$987.89		$1,065.2716	$1,065.27	$1,065.25	$1,065.30