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	$140.38	9.136%	$153.2051	$153.21	$153.20	$153.20
Purchase #2	$34.68	8.694%	$37.6951	$37.70	$37.70	$37.70
Purchase #3	$40.84	10.186%	$45	$45.00	$45.00	$45.00
Purchase #4	$86.60	13.865%	$98.6071	$98.61	$98.60	$98.60
Purchase #5	$208.71	6.820%	$222.944	$222.94	$222.95	$222.90
Purchase #6	$152.56	6.264%	$162.1164	$162.12	$162.10	$162.10
Purchase #7	$168.89	10.446%	$186.5322	$186.53	$186.55	$186.50
7 purchase totals =	$832.66		$906.0999	$906.11	$906.10	$906.00