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	$225.61	6.553%	$240.3942	$240.39	$240.40	$240.40
Purchase #2	$35.91	8.294%	$38.8884	$38.89	$38.90	$38.90
Purchase #3	$30.40	9.641%	$33.3309	$33.33	$33.35	$33.30
Purchase #4	$92.91	7.823%	$100.1783	$100.18	$100.20	$100.20
Purchase #5	$205.97	11.799%	$230.2724	$230.27	$230.25	$230.30
Purchase #6	$150.83	11.115%	$167.5948	$167.59	$167.60	$167.60
Purchase #7	$89.69	3.655%	$92.9682	$92.97	$92.95	$93.00
7 purchase totals =	$831.32		$903.6272	$903.62	$903.65	$903.70