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	$40.39	10.723%	$44.721	$44.72	$44.70	$44.70
Purchase #2	$236.31	7.855%	$254.8722	$254.87	$254.85	$254.90
Purchase #3	$182.48	7.850%	$196.8047	$196.80	$196.80	$196.80
Purchase #4	$112.76	13.368%	$127.8338	$127.83	$127.85	$127.80
Purchase #5	$176.62	4.373%	$184.3436	$184.34	$184.35	$184.30
Purchase #6	$120.27	9.515%	$131.7137	$131.71	$131.70	$131.70
Purchase #7	$140.36	9.292%	$153.4023	$153.40	$153.40	$153.40
7 purchase totals =	$1,009.19		$1,093.6913	$1,093.67	$1,093.65	$1,093.60