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	$170.43	9.867%	$187.2463	$187.25	$187.25	$187.20
Purchase #2	$52.39	4.276%	$54.6302	$54.63	$54.65	$54.60
Purchase #3	$119.89	7.157%	$128.4705	$128.47	$128.45	$128.50
Purchase #4	$71.29	11.784%	$79.6908	$79.69	$79.70	$79.70
Purchase #5	$163.49	5.552%	$172.567	$172.57	$172.55	$172.60
Purchase #6	$86.39	3.527%	$89.437	$89.44	$89.45	$89.40
Purchase #7	$132.88	6.493%	$141.5079	$141.51	$141.50	$141.50
7 purchase totals =	$796.76		$853.5497	$853.56	$853.55	$853.50