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	$22.55	8.480%	$24.4622	$24.46	$24.45	$24.50
Purchase #2	$86.66	11.805%	$96.8902	$96.89	$96.90	$96.90
Purchase #3	$38.89	12.110%	$43.5996	$43.60	$43.60	$43.60
Purchase #4	$159.34	10.189%	$175.5752	$175.58	$175.60	$175.60
Purchase #5	$49.41	13.502%	$56.0813	$56.08	$56.10	$56.10
Purchase #6	$81.77	9.767%	$89.7565	$89.76	$89.75	$89.80
Purchase #7	$123.73	3.604%	$128.1892	$128.19	$128.20	$128.20
7 purchase totals =	$562.35		$614.5542	$614.56	$614.60	$614.70