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	$13.67	5.850%	$14.4697	$14.47	$14.45	$14.50
Purchase #2	$63.55	11.814%	$71.0578	$71.06	$71.05	$71.10
Purchase #3	$72.98	13.121%	$82.5557	$82.56	$82.55	$82.60
Purchase #4	$37.96	10.816%	$42.0658	$42.07	$42.05	$42.10
Purchase #5	$181.32	3.630%	$187.9019	$187.90	$187.90	$187.90
Purchase #6	$230.83	12.759%	$260.2816	$260.28	$260.30	$260.30
Purchase #7	$177.66	10.680%	$196.6341	$196.63	$196.65	$196.60
7 purchase totals =	$777.97		$854.9666	$854.97	$854.95	$855.10