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	$243.27	10.718%	$269.3437	$269.34	$269.35	$269.30
Purchase #2	$123.66	7.181%	$132.54	$132.54	$132.55	$132.50
Purchase #3	$29.52	5.184%	$31.0503	$31.05	$31.05	$31.10
Purchase #4	$139.75	6.125%	$148.3097	$148.31	$148.30	$148.30
Purchase #5	$54.85	12.643%	$61.7847	$61.78	$61.80	$61.80
Purchase #6	$66.67	8.478%	$72.3223	$72.32	$72.30	$72.30
Purchase #7	$232.36	5.384%	$244.8703	$244.87	$244.85	$244.90
7 purchase totals =	$890.08		$960.2210	$960.21	$960.20	$960.20