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	$240.94	5.176%	$253.4111	$253.41	$253.40	$253.40
Purchase #2	$150.97	8.803%	$164.2599	$164.26	$164.25	$164.30
Purchase #3	$115.62	13.469%	$131.1929	$131.19	$131.20	$131.20
Purchase #4	$105.93	3.328%	$109.4554	$109.46	$109.45	$109.50
Purchase #5	$87.67	3.645%	$90.8656	$90.87	$90.85	$90.90
Purchase #6	$55.82	5.176%	$58.7092	$58.71	$58.70	$58.70
Purchase #7	$199.35	9.227%	$217.744	$217.74	$217.75	$217.70
7 purchase totals =	$956.30		$1,025.6381	$1,025.64	$1,025.60	$1,025.70