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	$66.62	9.444%	$72.9116	$72.91	$72.90	$72.90
Purchase #2	$203.36	5.172%	$213.8778	$213.88	$213.90	$213.90
Purchase #3	$5.33	10.161%	$5.8716	$5.87	$5.85	$5.90
Purchase #4	$124.85	5.188%	$131.3272	$131.33	$131.35	$131.30
Purchase #5	$128.60	12.637%	$144.8512	$144.85	$144.85	$144.90
Purchase #6	$151.52	10.342%	$167.1902	$167.19	$167.20	$167.20
Purchase #7	$206.90	11.729%	$231.1673	$231.17	$231.15	$231.20
7 purchase totals =	$887.18		$967.1969	$967.20	$967.20	$967.30