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	$135.89	5.243%	$143.0147	$143.01	$143.00	$143.00
Purchase #2	$135.92	5.629%	$143.5709	$143.57	$143.55	$143.60
Purchase #3	$35.31	10.139%	$38.8901	$38.89	$38.90	$38.90
Purchase #4	$92.63	9.542%	$101.4688	$101.47	$101.45	$101.50
Purchase #5	$216.79	3.359%	$224.072	$224.07	$224.05	$224.10
Purchase #6	$89.38	4.820%	$93.6881	$93.69	$93.70	$93.70
Purchase #7	$39.67	12.611%	$44.6728	$44.67	$44.65	$44.70
7 purchase totals =	$745.59		$789.3774	$789.37	$789.30	$789.50