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	$97.63	6.479%	$103.9554	$103.96	$103.95	$104.00
Purchase #2	$74.50	6.162%	$79.0907	$79.09	$79.10	$79.10
Purchase #3	$86.71	7.411%	$93.1361	$93.14	$93.15	$93.10
Purchase #4	$125.25	6.407%	$133.2748	$133.27	$133.25	$133.30
Purchase #5	$32.89	3.173%	$33.9336	$33.93	$33.95	$33.90
Purchase #6	$51.44	4.688%	$53.8515	$53.85	$53.85	$53.90
Purchase #7	$68.90	5.813%	$72.9052	$72.91	$72.90	$72.90
7 purchase totals =	$537.32		$570.1473	$570.15	$570.15	$570.20