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	$247.73	8.227%	$268.1107	$268.11	$268.10	$268.10
Purchase #2	$142.45	11.521%	$158.8617	$158.86	$158.85	$158.90
Purchase #3	$70.27	3.616%	$72.811	$72.81	$72.80	$72.80
Purchase #4	$126.46	10.294%	$139.4778	$139.48	$139.50	$139.50
Purchase #5	$230.90	3.495%	$238.97	$238.97	$238.95	$239.00
Purchase #6	$152.63	9.562%	$167.2245	$167.22	$167.20	$167.20
Purchase #7	$21.37	11.651%	$23.8598	$23.86	$23.85	$23.90
7 purchase totals =	$991.81		$1,069.3155	$1,069.31	$1,069.25	$1,069.40