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	$162.87	13.810%	$185.3623	$185.36	$185.35	$185.40
Purchase #2	$28.33	13.357%	$32.114	$32.11	$32.10	$32.10
Purchase #3	$195.31	13.866%	$222.3917	$222.39	$222.40	$222.40
Purchase #4	$248.92	13.768%	$283.1913	$283.19	$283.20	$283.20
Purchase #5	$207.93	8.337%	$225.2651	$225.27	$225.25	$225.30
Purchase #6	$187.69	10.550%	$207.4913	$207.49	$207.50	$207.50
Purchase #7	$64.36	5.484%	$67.8895	$67.89	$67.90	$67.90
7 purchase totals =	$1,095.41		$1,223.7052	$1,223.70	$1,223.70	$1,223.80