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	$136.52	10.318%	$150.6061	$150.61	$150.60	$150.60
Purchase #2	$24.86	9.703%	$27.2722	$27.27	$27.25	$27.30
Purchase #3	$196.58	3.461%	$203.3836	$203.38	$203.40	$203.40
Purchase #4	$238.56	13.739%	$271.3358	$271.34	$271.35	$271.30
Purchase #5	$90.59	10.198%	$99.8284	$99.83	$99.85	$99.80
Purchase #6	$130.94	11.184%	$145.5843	$145.58	$145.60	$145.60
Purchase #7	$43.73	9.533%	$47.8988	$47.90	$47.90	$47.90
7 purchase totals =	$861.78		$945.9092	$945.91	$945.95	$945.90