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	$233.59	10.716%	$258.6215	$258.62	$258.60	$258.60
Purchase #2	$219.81	9.147%	$239.916	$239.92	$239.90	$239.90
Purchase #3	$157.95	13.652%	$179.5133	$179.51	$179.50	$179.50
Purchase #4	$119.28	3.579%	$123.549	$123.55	$123.55	$123.50
Purchase #5	$210.92	12.668%	$237.6393	$237.64	$237.65	$237.60
Purchase #6	$12.32	9.795%	$13.5267	$13.53	$13.55	$13.50
Purchase #7	$7.96	6.490%	$8.4766	$8.48	$8.50	$8.50
7 purchase totals =	$961.83		$1,061.2424	$1,061.25	$1,061.25	$1,061.10