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	$203.32	9.627%	$222.8936	$222.89	$222.90	$222.90
Purchase #2	$158.95	7.536%	$170.9285	$170.93	$170.95	$170.90
Purchase #3	$40.97	3.617%	$42.4519	$42.45	$42.45	$42.50
Purchase #4	$192.86	13.651%	$219.1873	$219.19	$219.20	$219.20
Purchase #5	$143.41	10.378%	$158.2931	$158.29	$158.30	$158.30
Purchase #6	$67.89	7.854%	$73.2221	$73.22	$73.20	$73.20
Purchase #7	$128.99	3.467%	$133.4621	$133.46	$133.45	$133.50
7 purchase totals =	$936.39		$1,020.4386	$1,020.43	$1,020.45	$1,020.50