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	$214.63	6.828%	$229.2849	$229.28	$229.30	$229.30
Purchase #2	$162.89	4.261%	$169.8307	$169.83	$169.85	$169.80
Purchase #3	$51.83	4.497%	$54.1608	$54.16	$54.15	$54.20
Purchase #4	$132.41	12.147%	$148.4938	$148.49	$148.50	$148.50
Purchase #5	$185.67	5.853%	$196.5373	$196.54	$196.55	$196.50
Purchase #6	$125.50	8.742%	$136.4712	$136.47	$136.45	$136.50
Purchase #7	$166.31	8.235%	$180.0056	$180.01	$180.00	$180.00
7 purchase totals =	$1,039.24		$1,114.7843	$1,114.78	$1,114.80	$1,114.80