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	$70.42	3.138%	$72.6298	$72.63	$72.65	$72.60
Purchase #2	$115.80	13.844%	$131.8314	$131.83	$131.85	$131.80
Purchase #3	$22.85	13.444%	$25.922	$25.92	$25.90	$25.90
Purchase #4	$71.60	9.835%	$78.6419	$78.64	$78.65	$78.60
Purchase #5	$168.48	11.339%	$187.5839	$187.58	$187.60	$187.60
Purchase #6	$217.86	5.389%	$229.6005	$229.60	$229.60	$229.60
Purchase #7	$186.27	9.349%	$203.6844	$203.68	$203.70	$203.70
7 purchase totals =	$853.28		$929.8939	$929.88	$929.95	$929.80