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	$47.59	12.215%	$53.4031	$53.40	$53.40	$53.40
Purchase #2	$82.75	6.323%	$87.9823	$87.98	$88.00	$88.00
Purchase #3	$98.55	7.407%	$105.8496	$105.85	$105.85	$105.80
Purchase #4	$135.82	13.845%	$154.6243	$154.62	$154.60	$154.60
Purchase #5	$59.28	6.690%	$63.2458	$63.25	$63.25	$63.20
Purchase #6	$168.64	9.164%	$184.0942	$184.09	$184.10	$184.10
Purchase #7	$55.59	3.175%	$57.355	$57.36	$57.35	$57.40
7 purchase totals =	$648.22		$706.5543	$706.55	$706.55	$706.50