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	$29.39	10.778%	$32.5577	$32.56	$32.55	$32.60
Purchase #2	$88.28	12.426%	$99.2497	$99.25	$99.25	$99.20
Purchase #3	$19.47	8.145%	$21.0558	$21.06	$21.05	$21.10
Purchase #4	$138.41	6.847%	$147.8869	$147.89	$147.90	$147.90
Purchase #5	$35.69	12.113%	$40.0131	$40.01	$40.00	$40.00
Purchase #6	$124.38	10.404%	$137.3205	$137.32	$137.30	$137.30
Purchase #7	$191.73	3.545%	$198.5268	$198.53	$198.55	$198.50
7 purchase totals =	$627.35		$676.6105	$676.62	$676.60	$676.60