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	$99.83	11.548%	$111.3584	$111.36	$111.35	$111.40
Purchase #2	$57.32	13.712%	$65.1797	$65.18	$65.20	$65.20
Purchase #3	$147.38	10.313%	$162.5793	$162.58	$162.60	$162.60
Purchase #4	$169.46	8.661%	$184.1369	$184.14	$184.15	$184.10
Purchase #5	$170.55	5.419%	$179.7921	$179.79	$179.80	$179.80
Purchase #6	$162.37	7.118%	$173.9275	$173.93	$173.95	$173.90
Purchase #7	$198.84	4.651%	$208.088	$208.09	$208.10	$208.10
7 purchase totals =	$1,005.75		$1,085.0619	$1,085.07	$1,085.15	$1,085.10