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	$54.61	8.656%	$59.337	$59.34	$59.35	$59.30
Purchase #2	$182.79	8.642%	$198.5867	$198.59	$198.60	$198.60
Purchase #3	$176.47	9.115%	$192.5552	$192.56	$192.55	$192.60
Purchase #4	$61.78	8.131%	$66.8033	$66.80	$66.80	$66.80
Purchase #5	$229.67	7.630%	$247.1938	$247.19	$247.20	$247.20
Purchase #6	$88.66	8.394%	$96.1021	$96.10	$96.10	$96.10
Purchase #7	$135.88	5.622%	$143.5192	$143.52	$143.50	$143.50
7 purchase totals =	$929.86		$1,004.0973	$1,004.10	$1,004.10	$1,004.10