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	$177.38	5.645%	$187.3931	$187.39	$187.40	$187.40
Purchase #2	$63.75	7.495%	$68.5281	$68.53	$68.55	$68.50
Purchase #3	$86.51	10.479%	$95.5754	$95.58	$95.60	$95.60
Purchase #4	$170.56	10.280%	$188.0936	$188.09	$188.10	$188.10
Purchase #5	$66.29	9.114%	$72.3317	$72.33	$72.35	$72.30
Purchase #6	$62.63	13.487%	$71.0769	$71.08	$71.10	$71.10
Purchase #7	$26.66	10.284%	$29.4017	$29.40	$29.40	$29.40
7 purchase totals =	$653.78		$712.4005	$712.40	$712.50	$712.40