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	$215.89	10.503%	$238.5649	$238.56	$238.55	$238.60
Purchase #2	$156.56	7.243%	$167.8996	$167.90	$167.90	$167.90
Purchase #3	$182.78	12.553%	$205.7244	$205.72	$205.70	$205.70
Purchase #4	$129.84	12.624%	$146.231	$146.23	$146.25	$146.20
Purchase #5	$144.99	5.453%	$152.8963	$152.90	$152.90	$152.90
Purchase #6	$78.90	11.372%	$87.8725	$87.87	$87.85	$87.90
Purchase #7	$56.68	3.702%	$58.7783	$58.78	$58.80	$58.80
7 purchase totals =	$965.64		$1,057.9670	$1,057.96	$1,057.95	$1,058.00