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	$100.71	4.654%	$105.397	$105.40	$105.40	$105.40
Purchase #2	$40.53	10.360%	$44.7289	$44.73	$44.75	$44.70
Purchase #3	$231.81	4.343%	$241.8775	$241.88	$241.90	$241.90
Purchase #4	$136.76	10.854%	$151.6039	$151.60	$151.60	$151.60
Purchase #5	$196.64	13.281%	$222.7558	$222.76	$222.75	$222.80
Purchase #6	$95.29	8.467%	$103.3582	$103.36	$103.35	$103.40
Purchase #7	$35.67	3.685%	$36.9844	$36.98	$37.00	$37.00
7 purchase totals =	$837.41		$906.7057	$906.71	$906.75	$906.80