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	$114.94	7.204%	$123.2203	$123.22	$123.20	$123.20
Purchase #2	$202.94	10.670%	$224.5937	$224.59	$224.60	$224.60
Purchase #3	$86.96	3.340%	$89.8645	$89.86	$89.85	$89.90
Purchase #4	$158.74	3.581%	$164.4245	$164.42	$164.40	$164.40
Purchase #5	$11.90	11.596%	$13.2799	$13.28	$13.30	$13.30
Purchase #6	$213.65	4.418%	$223.0891	$223.09	$223.10	$223.10
Purchase #7	$196.94	9.478%	$215.606	$215.61	$215.60	$215.60
7 purchase totals =	$986.07		$1,054.0780	$1,054.07	$1,054.05	$1,054.10