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	$226.68	7.673%	$244.0732	$244.07	$244.05	$244.10
Purchase #2	$140.25	5.446%	$147.888	$147.89	$147.90	$147.90
Purchase #3	$138.42	10.455%	$152.8918	$152.89	$152.90	$152.90
Purchase #4	$81.93	10.662%	$90.6654	$90.67	$90.65	$90.70
Purchase #5	$135.87	10.678%	$150.3782	$150.38	$150.40	$150.40
Purchase #6	$49.31	10.532%	$54.5033	$54.50	$54.50	$54.50
Purchase #7	$78.77	12.400%	$88.5375	$88.54	$88.55	$88.50
7 purchase totals =	$851.23		$928.9374	$928.94	$928.95	$929.00