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	$175.37	9.242%	$191.5777	$191.58	$191.60	$191.60
Purchase #2	$80.53	12.212%	$90.3643	$90.36	$90.35	$90.40
Purchase #3	$162.43	12.437%	$182.6314	$182.63	$182.65	$182.60
Purchase #4	$71.55	13.710%	$81.3595	$81.36	$81.35	$81.40
Purchase #5	$158.83	5.597%	$167.7197	$167.72	$167.70	$167.70
Purchase #6	$54.93	4.192%	$57.2327	$57.23	$57.25	$57.20
Purchase #7	$173.27	5.579%	$182.9367	$182.94	$182.95	$182.90
7 purchase totals =	$876.91		$953.8220	$953.82	$953.85	$953.80