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	$189.49	3.761%	$196.6167	$196.62	$196.60	$196.60
Purchase #2	$20.83	5.603%	$21.9971	$22.00	$22.00	$22.00
Purchase #3	$168.66	5.714%	$178.2972	$178.30	$178.30	$178.30
Purchase #4	$40.84	3.134%	$42.1199	$42.12	$42.10	$42.10
Purchase #5	$130.57	13.689%	$148.4437	$148.44	$148.45	$148.40
Purchase #6	$201.64	11.584%	$224.998	$225.00	$225.00	$225.00
Purchase #7	$50.72	10.252%	$55.9198	$55.92	$55.90	$55.90
7 purchase totals =	$802.75		$868.3924	$868.40	$868.35	$868.30