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	$166.42	11.277%	$185.1872	$185.19	$185.20	$185.20
Purchase #2	$175.57	9.684%	$192.5722	$192.57	$192.55	$192.60
Purchase #3	$72.26	12.515%	$81.3033	$81.30	$81.30	$81.30
Purchase #4	$168.80	9.262%	$184.4343	$184.43	$184.45	$184.40
Purchase #5	$107.34	3.853%	$111.4758	$111.48	$111.50	$111.50
Purchase #6	$148.58	12.721%	$167.4809	$167.48	$167.50	$167.50
Purchase #7	$126.35	3.249%	$130.4551	$130.46	$130.45	$130.50
7 purchase totals =	$965.32		$1,052.9088	$1,052.91	$1,052.95	$1,053.00