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	$78.63	11.488%	$87.663	$87.66	$87.65	$87.70
Purchase #2	$209.94	12.853%	$236.9236	$236.92	$236.90	$236.90
Purchase #3	$11.39	13.673%	$12.9474	$12.95	$12.95	$12.90
Purchase #4	$203.52	3.405%	$210.4499	$210.45	$210.45	$210.40
Purchase #5	$167.99	6.660%	$179.1781	$179.18	$179.20	$179.20
Purchase #6	$184.65	8.726%	$200.7626	$200.76	$200.75	$200.80
Purchase #7	$77.78	6.143%	$82.558	$82.56	$82.55	$82.60
7 purchase totals =	$933.90		$1,010.4826	$1,010.48	$1,010.45	$1,010.50