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	$7.55	6.689%	$8.055	$8.06	$8.05	$8.10
Purchase #2	$31.66	5.665%	$33.4535	$33.45	$33.45	$33.50
Purchase #3	$208.50	7.202%	$223.5162	$223.52	$223.50	$223.50
Purchase #4	$137.84	6.346%	$146.5873	$146.59	$146.60	$146.60
Purchase #5	$188.45	5.287%	$198.4134	$198.41	$198.40	$198.40
Purchase #6	$117.52	8.375%	$127.3623	$127.36	$127.35	$127.40
Purchase #7	$204.79	5.728%	$216.5204	$216.52	$216.50	$216.50
7 purchase totals =	$896.31		$953.9081	$953.91	$953.85	$954.00