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	$145.49	3.614%	$150.748	$150.75	$150.75	$150.70
Purchase #2	$61.74	10.311%	$68.106	$68.11	$68.10	$68.10
Purchase #3	$116.83	5.262%	$122.9776	$122.98	$123.00	$123.00
Purchase #4	$47.60	4.478%	$49.7315	$49.73	$49.75	$49.70
Purchase #5	$11.73	9.187%	$12.8076	$12.81	$12.80	$12.80
Purchase #6	$141.31	6.486%	$150.4754	$150.48	$150.50	$150.50
Purchase #7	$101.40	11.335%	$112.8937	$112.89	$112.90	$112.90
7 purchase totals =	$626.10		$667.7398	$667.75	$667.80	$667.70