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	$161.45	10.265%	$178.0228	$178.02	$178.00	$178.00
Purchase #2	$193.59	3.298%	$199.9746	$199.97	$199.95	$200.00
Purchase #3	$109.83	12.384%	$123.4313	$123.43	$123.45	$123.40
Purchase #4	$51.29	10.282%	$56.5636	$56.56	$56.55	$56.60
Purchase #5	$250.30	4.120%	$260.6124	$260.61	$260.60	$260.60
Purchase #6	$70.29	10.700%	$77.811	$77.81	$77.80	$77.80
Purchase #7	$216.36	13.210%	$244.9412	$244.94	$244.95	$244.90
7 purchase totals =	$1,053.11		$1,141.3569	$1,141.34	$1,141.30	$1,141.30