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	$200.90	9.435%	$219.8549	$219.85	$219.85	$219.90
Purchase #2	$99.73	4.393%	$104.1111	$104.11	$104.10	$104.10
Purchase #3	$234.96	6.228%	$249.5933	$249.59	$249.60	$249.60
Purchase #4	$148.50	10.554%	$164.1727	$164.17	$164.15	$164.20
Purchase #5	$136.67	5.265%	$143.8657	$143.87	$143.85	$143.90
Purchase #6	$139.62	9.279%	$152.5753	$152.58	$152.60	$152.60
Purchase #7	$214.67	8.871%	$233.7134	$233.71	$233.70	$233.70
7 purchase totals =	$1,175.05		$1,267.8864	$1,267.88	$1,267.85	$1,268.00