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	$219.84	13.151%	$248.7512	$248.75	$248.75	$248.80
Purchase #2	$158.76	12.685%	$178.8987	$178.90	$178.90	$178.90
Purchase #3	$198.81	6.705%	$212.1402	$212.14	$212.15	$212.10
Purchase #4	$43.33	7.406%	$46.539	$46.54	$46.55	$46.50
Purchase #5	$38.45	10.626%	$42.5357	$42.54	$42.55	$42.50
Purchase #6	$241.57	5.715%	$255.3757	$255.38	$255.40	$255.40
Purchase #7	$22.58	7.521%	$24.2782	$24.28	$24.30	$24.30
7 purchase totals =	$923.34		$1,008.5187	$1,008.53	$1,008.60	$1,008.50