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	$58.60	10.257%	$64.6106	$64.61	$64.60	$64.60
Purchase #2	$142.92	9.776%	$156.8919	$156.89	$156.90	$156.90
Purchase #3	$240.61	13.561%	$273.2391	$273.24	$273.25	$273.20
Purchase #4	$69.74	3.748%	$72.3539	$72.35	$72.35	$72.40
Purchase #5	$103.34	11.322%	$115.0402	$115.04	$115.05	$115.00
Purchase #6	$126.96	4.829%	$133.0909	$133.09	$133.10	$133.10
Purchase #7	$210.33	5.393%	$221.6731	$221.67	$221.65	$221.70
7 purchase totals =	$952.50		$1,036.8997	$1,036.89	$1,036.90	$1,036.90