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	$33.86	10.676%	$37.4749	$37.47	$37.45	$37.50
Purchase #2	$233.29	13.756%	$265.3814	$265.38	$265.40	$265.40
Purchase #3	$167.76	6.713%	$179.0217	$179.02	$179.00	$179.00
Purchase #4	$16.71	5.501%	$17.6292	$17.63	$17.65	$17.60
Purchase #5	$67.64	6.773%	$72.2213	$72.22	$72.20	$72.20
Purchase #6	$77.57	10.395%	$85.6334	$85.63	$85.65	$85.60
Purchase #7	$79.56	13.234%	$90.089	$90.09	$90.10	$90.10
7 purchase totals =	$676.39		$747.4509	$747.44	$747.45	$747.40