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	$149.29	12.478%	$167.9184	$167.92	$167.90	$167.90
Purchase #2	$33.25	10.818%	$36.847	$36.85	$36.85	$36.80
Purchase #3	$46.25	11.271%	$51.4628	$51.46	$51.45	$51.50
Purchase #4	$78.71	13.837%	$89.6011	$89.60	$89.60	$89.60
Purchase #5	$214.77	4.844%	$225.1735	$225.17	$225.15	$225.20
Purchase #6	$176.57	8.661%	$191.8627	$191.86	$191.85	$191.90
Purchase #7	$68.55	8.838%	$74.6084	$74.61	$74.60	$74.60
7 purchase totals =	$767.39		$837.4739	$837.47	$837.40	$837.50