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	$112.73	6.327%	$119.8624	$119.86	$119.85	$119.90
Purchase #2	$204.27	11.545%	$227.853	$227.85	$227.85	$227.90
Purchase #3	$26.97	5.595%	$28.479	$28.48	$28.50	$28.50
Purchase #4	$160.38	11.774%	$179.2631	$179.26	$179.25	$179.30
Purchase #5	$201.71	12.508%	$226.9399	$226.94	$226.95	$226.90
Purchase #6	$227.78	12.491%	$256.232	$256.23	$256.25	$256.20
Purchase #7	$232.89	9.600%	$255.2474	$255.25	$255.25	$255.20
7 purchase totals =	$1,166.73		$1,293.8768	$1,293.87	$1,293.90	$1,293.90