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	$196.77	6.219%	$209.0071	$209.01	$209.00	$209.00
Purchase #2	$37.85	7.213%	$40.5801	$40.58	$40.60	$40.60
Purchase #3	$131.98	10.607%	$145.9791	$145.98	$146.00	$146.00
Purchase #4	$82.70	5.544%	$87.2849	$87.28	$87.30	$87.30
Purchase #5	$134.57	8.658%	$146.2211	$146.22	$146.20	$146.20
Purchase #6	$51.76	10.271%	$57.0763	$57.08	$57.10	$57.10
Purchase #7	$64.96	11.446%	$72.3953	$72.40	$72.40	$72.40
7 purchase totals =	$700.59		$758.5439	$758.55	$758.60	$758.60