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	$11.52	7.483%	$12.382	$12.38	$12.40	$12.40
Purchase #2	$219.66	7.519%	$236.1762	$236.18	$236.20	$236.20
Purchase #3	$196.34	9.603%	$215.1945	$215.19	$215.20	$215.20
Purchase #4	$238.47	6.700%	$254.4475	$254.45	$254.45	$254.40
Purchase #5	$161.35	4.504%	$168.6172	$168.62	$168.60	$168.60
Purchase #6	$83.59	8.679%	$90.8448	$90.84	$90.85	$90.80
Purchase #7	$127.40	4.671%	$133.3509	$133.35	$133.35	$133.40
7 purchase totals =	$1,038.33		$1,111.0131	$1,111.01	$1,111.05	$1,111.00