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	$244.97	13.572%	$278.2173	$278.22	$278.20	$278.20
Purchase #2	$10.94	4.267%	$11.4068	$11.41	$11.40	$11.40
Purchase #3	$136.95	9.600%	$150.0972	$150.10	$150.10	$150.10
Purchase #4	$186.35	11.162%	$207.1504	$207.15	$207.15	$207.20
Purchase #5	$53.37	12.219%	$59.8913	$59.89	$59.90	$59.90
Purchase #6	$79.68	12.147%	$89.3587	$89.36	$89.35	$89.40
Purchase #7	$198.32	5.433%	$209.0947	$209.09	$209.10	$209.10
7 purchase totals =	$910.58		$1,005.2164	$1,005.22	$1,005.20	$1,005.30