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	$228.60	11.615%	$255.1519	$255.15	$255.15	$255.20
Purchase #2	$13.64	10.471%	$15.0682	$15.07	$15.05	$15.10
Purchase #3	$50.64	8.653%	$55.0219	$55.02	$55.00	$55.00
Purchase #4	$242.53	4.383%	$253.1601	$253.16	$253.15	$253.20
Purchase #5	$184.56	8.308%	$199.8932	$199.89	$199.90	$199.90
Purchase #6	$99.94	4.816%	$104.7531	$104.75	$104.75	$104.80
Purchase #7	$246.79	4.486%	$257.861	$257.86	$257.85	$257.90
7 purchase totals =	$1,066.70		$1,140.9094	$1,140.90	$1,140.85	$1,141.10