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	$75.57	13.473%	$85.7515	$85.75	$85.75	$85.80
Purchase #2	$81.91	5.456%	$86.379	$86.38	$86.40	$86.40
Purchase #3	$97.89	5.558%	$103.3307	$103.33	$103.35	$103.30
Purchase #4	$50.62	12.766%	$57.0821	$57.08	$57.10	$57.10
Purchase #5	$80.66	7.241%	$86.5006	$86.50	$86.50	$86.50
Purchase #6	$14.76	5.709%	$15.6026	$15.60	$15.60	$15.60
Purchase #7	$174.82	13.863%	$199.0553	$199.06	$199.05	$199.10
7 purchase totals =	$576.23		$633.7018	$633.70	$633.75	$633.80