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	$37.52	3.264%	$38.7447	$38.74	$38.75	$38.70
Purchase #2	$88.27	9.204%	$96.3944	$96.39	$96.40	$96.40
Purchase #3	$6.82	8.687%	$7.4125	$7.41	$7.40	$7.40
Purchase #4	$236.30	6.588%	$251.8674	$251.87	$251.85	$251.90
Purchase #5	$229.42	8.620%	$249.196	$249.20	$249.20	$249.20
Purchase #6	$244.89	11.389%	$272.7805	$272.78	$272.80	$272.80
Purchase #7	$109.34	12.851%	$123.3913	$123.39	$123.40	$123.40
7 purchase totals =	$952.56		$1,039.7868	$1,039.78	$1,039.80	$1,039.80