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	$110.72	3.577%	$114.6805	$114.68	$114.70	$114.70
Purchase #2	$201.70	4.375%	$210.5244	$210.52	$210.50	$210.50
Purchase #3	$189.32	13.347%	$214.5885	$214.59	$214.60	$214.60
Purchase #4	$153.90	11.680%	$171.8755	$171.88	$171.90	$171.90
Purchase #5	$107.47	3.699%	$111.4453	$111.45	$111.45	$111.40
Purchase #6	$237.33	11.549%	$264.7392	$264.74	$264.75	$264.70
Purchase #7	$61.82	12.272%	$69.4066	$69.41	$69.40	$69.40
7 purchase totals =	$1,062.26		$1,157.2600	$1,157.27	$1,157.30	$1,157.20