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	$153.60	12.590%	$172.9382	$172.94	$172.95	$172.90
Purchase #2	$141.77	9.234%	$154.861	$154.86	$154.85	$154.90
Purchase #3	$137.37	13.797%	$156.3229	$156.32	$156.30	$156.30
Purchase #4	$116.67	10.171%	$128.5365	$128.54	$128.55	$128.50
Purchase #5	$41.78	4.725%	$43.7541	$43.75	$43.75	$43.80
Purchase #6	$117.89	6.216%	$125.218	$125.22	$125.20	$125.20
Purchase #7	$70.81	7.857%	$76.3735	$76.37	$76.35	$76.40
7 purchase totals =	$779.89		$858.0042	$858.00	$857.95	$858.00