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	$149.67	9.308%	$163.6013	$163.60	$163.60	$163.60
Purchase #2	$117.38	12.360%	$131.8882	$131.89	$131.90	$131.90
Purchase #3	$105.70	12.145%	$118.5373	$118.54	$118.55	$118.50
Purchase #4	$227.77	3.117%	$234.8696	$234.87	$234.85	$234.90
Purchase #5	$33.79	11.261%	$37.5951	$37.60	$37.60	$37.60
Purchase #6	$228.41	6.416%	$243.0648	$243.06	$243.05	$243.10
Purchase #7	$151.90	3.300%	$156.9127	$156.91	$156.90	$156.90
7 purchase totals =	$1,014.62		$1,086.4690	$1,086.47	$1,086.45	$1,086.50