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	$91.89	3.102%	$94.7404	$94.74	$94.75	$94.70
Purchase #2	$43.60	12.169%	$48.9057	$48.91	$48.90	$48.90
Purchase #3	$38.81	4.427%	$40.5281	$40.53	$40.55	$40.50
Purchase #4	$56.95	8.602%	$61.8488	$61.85	$61.85	$61.80
Purchase #5	$152.97	12.299%	$171.7838	$171.78	$171.80	$171.80
Purchase #6	$45.60	7.125%	$48.849	$48.85	$48.85	$48.80
Purchase #7	$100.98	6.185%	$107.2256	$107.23	$107.25	$107.20
7 purchase totals =	$530.80		$573.8814	$573.89	$573.95	$573.70