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	$24.76	3.655%	$25.665	$25.67	$25.65	$25.70
Purchase #2	$68.64	13.746%	$78.0753	$78.08	$78.10	$78.10
Purchase #3	$42.53	7.443%	$45.6955	$45.70	$45.70	$45.70
Purchase #4	$91.58	8.728%	$99.5731	$99.57	$99.55	$99.60
Purchase #5	$10.89	4.321%	$11.3606	$11.36	$11.35	$11.40
Purchase #6	$217.31	3.409%	$224.7181	$224.72	$224.70	$224.70
Purchase #7	$163.47	7.207%	$175.2513	$175.25	$175.25	$175.30
7 purchase totals =	$619.18		$660.3389	$660.35	$660.30	$660.50