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	$94.51	5.118%	$99.347	$99.35	$99.35	$99.30
Purchase #2	$177.66	5.419%	$187.2874	$187.29	$187.30	$187.30
Purchase #3	$18.94	13.389%	$21.4759	$21.48	$21.50	$21.50
Purchase #4	$89.47	7.461%	$96.1454	$96.15	$96.15	$96.10
Purchase #5	$63.67	6.729%	$67.9544	$67.95	$67.95	$68.00
Purchase #6	$11.92	5.854%	$12.6178	$12.62	$12.60	$12.60
Purchase #7	$35.29	9.633%	$38.6895	$38.69	$38.70	$38.70
7 purchase totals =	$491.46		$523.5174	$523.53	$523.55	$523.50