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	$190.46	9.268%	$208.1118	$208.11	$208.10	$208.10
Purchase #2	$214.63	3.628%	$222.4168	$222.42	$222.40	$222.40
Purchase #3	$157.82	8.363%	$171.0185	$171.02	$171.00	$171.00
Purchase #4	$111.85	6.781%	$119.4345	$119.43	$119.45	$119.40
Purchase #5	$88.46	8.361%	$95.8561	$95.86	$95.85	$95.90
Purchase #6	$206.47	12.866%	$233.0344	$233.03	$233.05	$233.00
Purchase #7	$59.84	12.223%	$67.1542	$67.15	$67.15	$67.20
7 purchase totals =	$1,029.53		$1,117.0263	$1,117.02	$1,117.00	$1,117.00