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	$74.42	11.208%	$82.761	$82.76	$82.75	$82.80
Purchase #2	$86.32	5.209%	$90.8164	$90.82	$90.80	$90.80
Purchase #3	$137.72	12.162%	$154.4695	$154.47	$154.45	$154.50
Purchase #4	$208.99	7.310%	$224.2672	$224.27	$224.25	$224.30
Purchase #5	$196.36	9.404%	$214.8257	$214.83	$214.85	$214.80
Purchase #6	$160.97	3.292%	$166.2691	$166.27	$166.25	$166.30
Purchase #7	$201.56	8.181%	$218.0496	$218.05	$218.05	$218.00
7 purchase totals =	$1,066.34		$1,151.4585	$1,151.47	$1,151.40	$1,151.50