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	$156.92	12.689%	$176.8316	$176.83	$176.85	$176.80
Purchase #2	$59.38	3.402%	$61.4001	$61.40	$61.40	$61.40
Purchase #3	$143.29	3.734%	$148.6404	$148.64	$148.65	$148.60
Purchase #4	$237.79	6.554%	$253.3748	$253.37	$253.35	$253.40
Purchase #5	$129.83	5.169%	$136.5409	$136.54	$136.55	$136.50
Purchase #6	$203.65	5.704%	$215.2662	$215.27	$215.25	$215.30
Purchase #7	$107.68	5.361%	$113.4527	$113.45	$113.45	$113.50
7 purchase totals =	$1,038.54		$1,105.5067	$1,105.50	$1,105.50	$1,105.50