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	$215.78	11.428%	$240.4393	$240.44	$240.45	$240.40
Purchase #2	$87.44	3.726%	$90.698	$90.70	$90.70	$90.70
Purchase #3	$36.44	8.407%	$39.5035	$39.50	$39.50	$39.50
Purchase #4	$122.47	12.127%	$137.3219	$137.32	$137.30	$137.30
Purchase #5	$88.60	3.293%	$91.5176	$91.52	$91.50	$91.50
Purchase #6	$139.80	11.134%	$155.3653	$155.37	$155.35	$155.40
Purchase #7	$229.57	13.370%	$260.2635	$260.26	$260.25	$260.30
7 purchase totals =	$920.10		$1,015.1091	$1,015.11	$1,015.05	$1,015.10