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	$138.43	5.170%	$145.5868	$145.59	$145.60	$145.60
Purchase #2	$179.50	4.674%	$187.8898	$187.89	$187.90	$187.90
Purchase #3	$159.63	8.166%	$172.6654	$172.67	$172.65	$172.70
Purchase #4	$104.30	4.466%	$108.958	$108.96	$108.95	$109.00
Purchase #5	$19.76	11.560%	$22.0443	$22.04	$22.05	$22.00
Purchase #6	$56.33	7.481%	$60.544	$60.54	$60.55	$60.50
Purchase #7	$151.81	7.278%	$162.8587	$162.86	$162.85	$162.90
7 purchase totals =	$809.76		$860.5470	$860.55	$860.55	$860.60