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	$6.56	10.864%	$7.2727	$7.27	$7.25	$7.30
Purchase #2	$95.63	7.456%	$102.7602	$102.76	$102.75	$102.80
Purchase #3	$236.31	7.181%	$253.2794	$253.28	$253.30	$253.30
Purchase #4	$186.41	4.735%	$195.2365	$195.24	$195.25	$195.20
Purchase #5	$117.67	5.238%	$123.8336	$123.83	$123.85	$123.80
Purchase #6	$142.28	7.246%	$152.5896	$152.59	$152.60	$152.60
Purchase #7	$209.98	4.275%	$218.9566	$218.96	$218.95	$219.00
7 purchase totals =	$994.84		$1,053.9286	$1,053.93	$1,053.95	$1,054.00