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	$235.63	7.555%	$253.4318	$253.43	$253.45	$253.40
Purchase #2	$72.99	11.788%	$81.5941	$81.59	$81.60	$81.60
Purchase #3	$104.66	3.608%	$108.4361	$108.44	$108.45	$108.40
Purchase #4	$137.86	10.446%	$152.2609	$152.26	$152.25	$152.30
Purchase #5	$135.77	10.840%	$150.4875	$150.49	$150.50	$150.50
Purchase #6	$60.59	9.234%	$66.1849	$66.18	$66.20	$66.20
Purchase #7	$118.26	11.168%	$131.4673	$131.47	$131.45	$131.50
7 purchase totals =	$865.76		$943.8626	$943.86	$943.90	$943.90