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	$72.54	3.214%	$74.8714	$74.87	$74.85	$74.90
Purchase #2	$122.65	7.549%	$131.9088	$131.91	$131.90	$131.90
Purchase #3	$171.96	5.344%	$181.1495	$181.15	$181.15	$181.10
Purchase #4	$200.74	9.523%	$219.8565	$219.86	$219.85	$219.90
Purchase #5	$67.37	8.664%	$73.2069	$73.21	$73.20	$73.20
Purchase #6	$78.84	4.218%	$82.1655	$82.17	$82.15	$82.20
Purchase #7	$150.50	13.291%	$170.503	$170.50	$170.50	$170.50
7 purchase totals =	$864.60		$933.6616	$933.67	$933.60	$933.70