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	$82.35	10.481%	$90.9811	$90.98	$91.00	$91.00
Purchase #2	$229.33	5.248%	$241.3652	$241.37	$241.35	$241.40
Purchase #3	$108.75	9.769%	$119.3738	$119.37	$119.35	$119.40
Purchase #4	$19.57	3.591%	$20.2728	$20.27	$20.25	$20.30
Purchase #5	$169.72	8.639%	$184.3821	$184.38	$184.40	$184.40
Purchase #6	$249.68	13.542%	$283.4917	$283.49	$283.50	$283.50
Purchase #7	$91.67	9.410%	$100.2961	$100.30	$100.30	$100.30
7 purchase totals =	$951.07		$1,040.1628	$1,040.16	$1,040.15	$1,040.30