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	$63.96	13.239%	$72.4277	$72.43	$72.45	$72.40
Purchase #2	$15.73	13.846%	$17.908	$17.91	$17.90	$17.90
Purchase #3	$178.83	6.664%	$190.7472	$190.75	$190.75	$190.70
Purchase #4	$225.72	11.102%	$250.7794	$250.78	$250.80	$250.80
Purchase #5	$74.60	10.539%	$82.4621	$82.46	$82.45	$82.50
Purchase #6	$177.63	12.173%	$199.2529	$199.25	$199.25	$199.30
Purchase #7	$61.72	3.268%	$63.737	$63.74	$63.75	$63.70
7 purchase totals =	$798.19		$877.3143	$877.32	$877.35	$877.30