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	$237.90	6.471%	$253.2945	$253.29	$253.30	$253.30
Purchase #2	$92.32	13.711%	$104.978	$104.98	$105.00	$105.00
Purchase #3	$228.51	5.388%	$240.8221	$240.82	$240.80	$240.80
Purchase #4	$31.63	6.263%	$33.611	$33.61	$33.60	$33.60
Purchase #5	$190.27	5.409%	$200.5617	$200.56	$200.55	$200.60
Purchase #6	$232.53	10.778%	$257.5921	$257.59	$257.60	$257.60
Purchase #7	$231.97	9.106%	$253.0932	$253.09	$253.10	$253.10
7 purchase totals =	$1,245.13		$1,343.9526	$1,343.94	$1,343.95	$1,344.00