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	$102.43	5.761%	$108.331	$108.33	$108.35	$108.30
Purchase #2	$25.36	3.591%	$26.2707	$26.27	$26.25	$26.30
Purchase #3	$9.54	8.281%	$10.33	$10.33	$10.35	$10.30
Purchase #4	$59.67	12.296%	$67.007	$67.01	$67.00	$67.00
Purchase #5	$143.94	3.356%	$148.7706	$148.77	$148.75	$148.80
Purchase #6	$42.96	4.348%	$44.8279	$44.83	$44.85	$44.80
Purchase #7	$126.79	4.725%	$132.7808	$132.78	$132.80	$132.80
7 purchase totals =	$510.69		$538.3180	$538.32	$538.35	$538.30