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	$50.61	11.211%	$56.2839	$56.28	$56.30	$56.30
Purchase #2	$12.60	7.517%	$13.5471	$13.55	$13.55	$13.50
Purchase #3	$59.43	8.449%	$64.4512	$64.45	$64.45	$64.50
Purchase #4	$205.64	13.739%	$233.8929	$233.89	$233.90	$233.90
Purchase #5	$141.56	7.683%	$152.4361	$152.44	$152.45	$152.40
Purchase #6	$189.51	3.430%	$196.0102	$196.01	$196.00	$196.00
Purchase #7	$74.58	5.425%	$78.626	$78.63	$78.65	$78.60
7 purchase totals =	$733.93		$795.2474	$795.25	$795.30	$795.20