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	$169.29	8.623%	$183.8879	$183.89	$183.90	$183.90
Purchase #2	$130.43	8.766%	$141.8635	$141.86	$141.85	$141.90
Purchase #3	$38.42	9.106%	$41.9185	$41.92	$41.90	$41.90
Purchase #4	$40.97	4.360%	$42.7563	$42.76	$42.75	$42.80
Purchase #5	$146.37	3.419%	$151.3744	$151.37	$151.35	$151.40
Purchase #6	$232.79	3.736%	$241.487	$241.49	$241.50	$241.50
Purchase #7	$59.61	4.268%	$62.1542	$62.15	$62.15	$62.20
7 purchase totals =	$817.88		$865.4418	$865.44	$865.40	$865.60