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	$101.25	9.785%	$111.1573	$111.16	$111.15	$111.20
Purchase #2	$179.53	8.441%	$194.6841	$194.68	$194.70	$194.70
Purchase #3	$204.78	5.271%	$215.574	$215.57	$215.55	$215.60
Purchase #4	$168.43	7.235%	$180.6159	$180.62	$180.60	$180.60
Purchase #5	$150.72	7.132%	$161.4694	$161.47	$161.45	$161.50
Purchase #6	$82.66	8.619%	$89.7845	$89.78	$89.80	$89.80
Purchase #7	$109.32	7.869%	$117.9224	$117.92	$117.90	$117.90
7 purchase totals =	$996.69		$1,071.2076	$1,071.20	$1,071.15	$1,071.30