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	$22.63	9.119%	$24.6936	$24.69	$24.70	$24.70
Purchase #2	$101.33	3.512%	$104.8887	$104.89	$104.90	$104.90
Purchase #3	$205.58	12.788%	$231.8696	$231.87	$231.85	$231.90
Purchase #4	$31.83	4.416%	$33.2356	$33.24	$33.25	$33.20
Purchase #5	$106.58	4.323%	$111.1875	$111.19	$111.20	$111.20
Purchase #6	$53.83	3.874%	$55.9154	$55.92	$55.90	$55.90
Purchase #7	$182.91	5.481%	$192.9353	$192.94	$192.95	$192.90
7 purchase totals =	$704.69		$754.7257	$754.74	$754.75	$754.70