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	$166.97	7.441%	$179.3942	$179.39	$179.40	$179.40
Purchase #2	$99.37	9.109%	$108.4216	$108.42	$108.40	$108.40
Purchase #3	$230.78	5.127%	$242.6121	$242.61	$242.60	$242.60
Purchase #4	$126.59	7.561%	$136.1615	$136.16	$136.15	$136.20
Purchase #5	$81.52	10.698%	$90.241	$90.24	$90.25	$90.20
Purchase #6	$67.51	8.662%	$73.3577	$73.36	$73.35	$73.40
Purchase #7	$172.59	13.618%	$196.0933	$196.09	$196.10	$196.10
7 purchase totals =	$945.33		$1,026.2814	$1,026.27	$1,026.25	$1,026.30