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	$147.81	11.275%	$164.4756	$164.48	$164.50	$164.50
Purchase #2	$244.81	7.172%	$262.3678	$262.37	$262.35	$262.40
Purchase #3	$88.30	5.139%	$92.8377	$92.84	$92.85	$92.80
Purchase #4	$69.36	5.128%	$72.9168	$72.92	$72.90	$72.90
Purchase #5	$52.76	8.859%	$57.434	$57.43	$57.45	$57.40
Purchase #6	$155.60	9.458%	$170.3166	$170.32	$170.30	$170.30
Purchase #7	$177.57	3.350%	$183.5186	$183.52	$183.50	$183.50
7 purchase totals =	$936.21		$1,003.8671	$1,003.88	$1,003.85	$1,003.80