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	$209.67	7.540%	$225.4791	$225.48	$225.50	$225.50
Purchase #2	$250.26	7.718%	$269.5751	$269.58	$269.60	$269.60
Purchase #3	$187.90	5.598%	$198.4186	$198.42	$198.40	$198.40
Purchase #4	$119.52	6.580%	$127.3844	$127.38	$127.40	$127.40
Purchase #5	$75.28	7.147%	$80.6603	$80.66	$80.65	$80.70
Purchase #6	$181.36	6.254%	$192.7023	$192.70	$192.70	$192.70
Purchase #7	$40.72	11.414%	$45.3678	$45.37	$45.35	$45.40
7 purchase totals =	$1,064.71		$1,139.5876	$1,139.59	$1,139.60	$1,139.70