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	$68.72	4.102%	$71.5389	$71.54	$71.55	$71.50
Purchase #2	$102.75	13.827%	$116.9572	$116.96	$116.95	$117.00
Purchase #3	$150.88	13.449%	$171.1719	$171.17	$171.15	$171.20
Purchase #4	$95.39	3.713%	$98.9318	$98.93	$98.95	$98.90
Purchase #5	$56.40	5.356%	$59.4208	$59.42	$59.40	$59.40
Purchase #6	$34.42	6.281%	$36.5819	$36.58	$36.60	$36.60
Purchase #7	$136.69	12.443%	$153.6983	$153.70	$153.70	$153.70
7 purchase totals =	$645.25		$708.3008	$708.30	$708.30	$708.30