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	$171.82	13.171%	$194.4504	$194.45	$194.45	$194.50
Purchase #2	$55.92	7.279%	$59.9904	$59.99	$60.00	$60.00
Purchase #3	$29.83	11.605%	$33.2918	$33.29	$33.30	$33.30
Purchase #4	$10.45	10.277%	$11.5239	$11.52	$11.50	$11.50
Purchase #5	$72.37	5.629%	$76.4437	$76.44	$76.45	$76.40
Purchase #6	$246.59	9.484%	$269.9766	$269.98	$270.00	$270.00
Purchase #7	$150.73	9.307%	$164.7584	$164.76	$164.75	$164.80
7 purchase totals =	$737.71		$810.4352	$810.43	$810.45	$810.50