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	$160.48	10.580%	$177.4588	$177.46	$177.45	$177.50
Purchase #2	$55.48	12.412%	$62.3662	$62.37	$62.35	$62.40
Purchase #3	$100.38	3.180%	$103.5721	$103.57	$103.55	$103.60
Purchase #4	$209.49	11.595%	$233.7804	$233.78	$233.80	$233.80
Purchase #5	$42.81	3.268%	$44.209	$44.21	$44.20	$44.20
Purchase #6	$55.28	11.464%	$61.6173	$61.62	$61.60	$61.60
Purchase #7	$234.89	10.654%	$259.9152	$259.92	$259.90	$259.90
7 purchase totals =	$858.81		$942.9190	$942.93	$942.85	$943.00