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	$155.86	12.520%	$175.3737	$175.37	$175.35	$175.40
Purchase #2	$220.74	5.605%	$233.1125	$233.11	$233.10	$233.10
Purchase #3	$72.52	5.507%	$76.5137	$76.51	$76.50	$76.50
Purchase #4	$28.32	5.208%	$29.7949	$29.79	$29.80	$29.80
Purchase #5	$99.38	13.783%	$113.0775	$113.08	$113.10	$113.10
Purchase #6	$52.79	12.367%	$59.3185	$59.32	$59.30	$59.30
Purchase #7	$49.32	10.484%	$54.4907	$54.49	$54.50	$54.50
7 purchase totals =	$678.93		$741.6815	$741.67	$741.65	$741.70