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	$39.69	12.441%	$44.6278	$44.63	$44.65	$44.60
Purchase #2	$176.61	11.510%	$196.9378	$196.94	$196.95	$196.90
Purchase #3	$62.73	12.352%	$70.4784	$70.48	$70.50	$70.50
Purchase #4	$80.85	7.139%	$86.6219	$86.62	$86.60	$86.60
Purchase #5	$141.53	7.869%	$152.667	$152.67	$152.65	$152.70
Purchase #6	$29.43	9.687%	$32.2809	$32.28	$32.30	$32.30
Purchase #7	$114.90	6.163%	$121.9813	$121.98	$122.00	$122.00
7 purchase totals =	$645.74		$705.5951	$705.60	$705.65	$705.60