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	$36.52	4.417%	$38.1331	$38.13	$38.15	$38.10
Purchase #2	$235.93	6.143%	$250.4232	$250.42	$250.40	$250.40
Purchase #3	$121.37	10.175%	$133.7194	$133.72	$133.70	$133.70
Purchase #4	$225.47	10.712%	$249.6223	$249.62	$249.60	$249.60
Purchase #5	$122.54	6.742%	$130.8016	$130.80	$130.80	$130.80
Purchase #6	$175.28	12.191%	$196.6484	$196.65	$196.65	$196.60
Purchase #7	$100.74	4.144%	$104.9147	$104.91	$104.90	$104.90
7 purchase totals =	$1,017.85		$1,104.2627	$1,104.25	$1,104.20	$1,104.10