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	$132.72	6.263%	$141.0323	$141.03	$141.05	$141.00
Purchase #2	$44.61	13.275%	$50.532	$50.53	$50.55	$50.50
Purchase #3	$133.92	5.300%	$141.0178	$141.02	$141.00	$141.00
Purchase #4	$107.83	11.856%	$120.6143	$120.61	$120.60	$120.60
Purchase #5	$136.53	13.177%	$154.5206	$154.52	$154.50	$154.50
Purchase #6	$152.95	12.616%	$172.2462	$172.25	$172.25	$172.20
Purchase #7	$54.53	4.546%	$57.0089	$57.01	$57.00	$57.00
7 purchase totals =	$763.09		$836.9721	$836.97	$836.95	$836.80