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	$156.86	3.599%	$162.5054	$162.51	$162.50	$162.50
Purchase #2	$74.50	5.146%	$78.3338	$78.33	$78.35	$78.30
Purchase #3	$80.94	13.108%	$91.5496	$91.55	$91.55	$91.50
Purchase #4	$43.63	11.459%	$48.6296	$48.63	$48.65	$48.60
Purchase #5	$177.30	3.390%	$183.3105	$183.31	$183.30	$183.30
Purchase #6	$160.89	7.547%	$173.0324	$173.03	$173.05	$173.00
Purchase #7	$182.34	4.283%	$190.1496	$190.15	$190.15	$190.10
7 purchase totals =	$876.46		$927.5109	$927.51	$927.55	$927.30