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	$55.79	10.581%	$61.6931	$61.69	$61.70	$61.70
Purchase #2	$224.49	11.783%	$250.9417	$250.94	$250.95	$250.90
Purchase #3	$159.48	10.243%	$175.8155	$175.82	$175.80	$175.80
Purchase #4	$201.28	3.471%	$208.2664	$208.27	$208.25	$208.30
Purchase #5	$174.65	10.287%	$192.6162	$192.62	$192.60	$192.60
Purchase #6	$118.91	4.639%	$124.4262	$124.43	$124.45	$124.40
Purchase #7	$40.83	6.634%	$43.5387	$43.54	$43.55	$43.50
7 purchase totals =	$975.43		$1,057.2978	$1,057.31	$1,057.30	$1,057.20