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	$146.91	3.430%	$151.949	$151.95	$151.95	$151.90
Purchase #2	$154.27	6.773%	$164.7187	$164.72	$164.70	$164.70
Purchase #3	$69.61	3.463%	$72.0206	$72.02	$72.00	$72.00
Purchase #4	$152.97	10.707%	$169.3485	$169.35	$169.35	$169.30
Purchase #5	$187.96	9.619%	$206.0399	$206.04	$206.05	$206.00
Purchase #6	$66.25	8.816%	$72.0906	$72.09	$72.10	$72.10
Purchase #7	$51.55	11.400%	$57.4267	$57.43	$57.45	$57.40
7 purchase totals =	$829.52		$893.5940	$893.60	$893.60	$893.40