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	$77.94	10.868%	$86.4105	$86.41	$86.40	$86.40
Purchase #2	$227.55	4.333%	$237.4097	$237.41	$237.40	$237.40
Purchase #3	$99.95	11.671%	$111.6152	$111.62	$111.60	$111.60
Purchase #4	$158.87	3.244%	$164.0237	$164.02	$164.00	$164.00
Purchase #5	$216.38	3.158%	$223.2133	$223.21	$223.20	$223.20
Purchase #6	$36.98	7.743%	$39.8434	$39.84	$39.85	$39.80
Purchase #7	$151.62	11.494%	$169.0472	$169.05	$169.05	$169.00
7 purchase totals =	$969.29		$1,031.5630	$1,031.56	$1,031.50	$1,031.40