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	$26.85	5.484%	$28.3225	$28.32	$28.30	$28.30
Purchase #2	$190.64	7.785%	$205.4813	$205.48	$205.50	$205.50
Purchase #3	$74.45	11.815%	$83.2463	$83.25	$83.25	$83.20
Purchase #4	$85.83	10.110%	$94.5074	$94.51	$94.50	$94.50
Purchase #5	$147.76	11.207%	$164.3195	$164.32	$164.30	$164.30
Purchase #6	$225.89	5.469%	$238.2439	$238.24	$238.25	$238.20
Purchase #7	$93.60	8.873%	$101.9051	$101.91	$101.90	$101.90
7 purchase totals =	$845.02		$916.0260	$916.03	$916.00	$915.90