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	$127.94	3.355%	$132.2324	$132.23	$132.25	$132.20
Purchase #2	$84.67	5.762%	$89.5487	$89.55	$89.55	$89.50
Purchase #3	$241.78	7.288%	$259.4009	$259.40	$259.40	$259.40
Purchase #4	$132.89	3.592%	$137.6634	$137.66	$137.65	$137.70
Purchase #5	$112.97	9.238%	$123.4062	$123.41	$123.40	$123.40
Purchase #6	$223.95	3.741%	$232.328	$232.33	$232.35	$232.30
Purchase #7	$132.83	11.425%	$148.0058	$148.01	$148.00	$148.00
7 purchase totals =	$1,057.03		$1,122.5854	$1,122.59	$1,122.60	$1,122.50