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	$63.89	13.582%	$72.5675	$72.57	$72.55	$72.60
Purchase #2	$32.52	8.481%	$35.278	$35.28	$35.30	$35.30
Purchase #3	$224.48	7.198%	$240.6381	$240.64	$240.65	$240.60
Purchase #4	$5.49	12.606%	$6.1821	$6.18	$6.20	$6.20
Purchase #5	$181.91	5.254%	$191.4676	$191.47	$191.45	$191.50
Purchase #6	$95.82	5.280%	$100.8793	$100.88	$100.90	$100.90
Purchase #7	$13.92	12.643%	$15.6799	$15.68	$15.70	$15.70
7 purchase totals =	$618.03		$662.6925	$662.70	$662.75	$662.80