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	$129.58	10.264%	$142.8801	$142.88	$142.90	$142.90
Purchase #2	$94.74	9.340%	$103.5887	$103.59	$103.60	$103.60
Purchase #3	$34.28	3.489%	$35.476	$35.48	$35.50	$35.50
Purchase #4	$240.91	8.112%	$260.4526	$260.45	$260.45	$260.50
Purchase #5	$44.84	8.436%	$48.6227	$48.62	$48.60	$48.60
Purchase #6	$98.68	5.531%	$104.138	$104.14	$104.15	$104.10
Purchase #7	$32.88	13.659%	$37.3711	$37.37	$37.35	$37.40
7 purchase totals =	$675.91		$732.5292	$732.53	$732.55	$732.60