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	$210.93	7.660%	$227.0872	$227.09	$227.10	$227.10
Purchase #2	$87.82	3.450%	$90.8498	$90.85	$90.85	$90.80
Purchase #3	$149.31	11.186%	$166.0118	$166.01	$166.00	$166.00
Purchase #4	$21.99	13.166%	$24.8852	$24.89	$24.90	$24.90
Purchase #5	$65.84	8.802%	$71.6352	$71.64	$71.65	$71.60
Purchase #6	$77.69	3.625%	$80.5063	$80.51	$80.50	$80.50
Purchase #7	$85.98	12.376%	$96.6209	$96.62	$96.60	$96.60
7 purchase totals =	$699.56		$757.5964	$757.61	$757.60	$757.50