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	$65.89	9.175%	$71.9354	$71.94	$71.95	$71.90
Purchase #2	$48.62	9.801%	$53.3852	$53.39	$53.40	$53.40
Purchase #3	$190.93	6.800%	$203.9132	$203.91	$203.90	$203.90
Purchase #4	$222.88	9.661%	$244.4124	$244.41	$244.40	$244.40
Purchase #5	$41.51	9.422%	$45.4211	$45.42	$45.40	$45.40
Purchase #6	$61.27	5.249%	$64.4861	$64.49	$64.50	$64.50
Purchase #7	$43.64	6.540%	$46.4941	$46.49	$46.50	$46.50
7 purchase totals =	$674.74		$730.0475	$730.05	$730.05	$730.00