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	$132.35	10.866%	$146.7312	$146.73	$146.75	$146.70
Purchase #2	$52.49	12.554%	$59.0796	$59.08	$59.10	$59.10
Purchase #3	$71.54	7.497%	$76.9034	$76.90	$76.90	$76.90
Purchase #4	$107.78	6.562%	$114.8525	$114.85	$114.85	$114.90
Purchase #5	$190.87	13.498%	$216.6336	$216.63	$216.65	$216.60
Purchase #6	$105.30	6.726%	$112.3825	$112.38	$112.40	$112.40
Purchase #7	$242.91	6.382%	$258.4125	$258.41	$258.40	$258.40
7 purchase totals =	$903.24		$984.9953	$984.98	$985.05	$985.00