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	$162.84	12.721%	$183.5549	$183.55	$183.55	$183.60
Purchase #2	$109.83	12.743%	$123.8256	$123.83	$123.85	$123.80
Purchase #3	$184.79	3.574%	$191.3944	$191.39	$191.40	$191.40
Purchase #4	$130.88	9.325%	$143.0846	$143.08	$143.10	$143.10
Purchase #5	$163.34	9.453%	$178.7805	$178.78	$178.80	$178.80
Purchase #6	$81.96	10.722%	$90.7478	$90.75	$90.75	$90.70
Purchase #7	$100.75	9.133%	$109.9515	$109.95	$109.95	$110.00
7 purchase totals =	$934.39		$1,021.3393	$1,021.33	$1,021.40	$1,021.40