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	$41.63	5.295%	$43.8343	$43.83	$43.85	$43.80
Purchase #2	$35.92	4.362%	$37.4868	$37.49	$37.50	$37.50
Purchase #3	$75.77	6.643%	$80.8034	$80.80	$80.80	$80.80
Purchase #4	$249.34	3.255%	$257.456	$257.46	$257.45	$257.50
Purchase #5	$66.61	7.526%	$71.6231	$71.62	$71.60	$71.60
Purchase #6	$119.67	4.614%	$125.1916	$125.19	$125.20	$125.20
Purchase #7	$143.84	3.510%	$148.8888	$148.89	$148.90	$148.90
7 purchase totals =	$732.78		$765.2840	$765.28	$765.30	$765.30