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	$44.31	3.269%	$45.7585	$45.76	$45.75	$45.80
Purchase #2	$73.81	11.655%	$82.4126	$82.41	$82.40	$82.40
Purchase #3	$103.72	9.749%	$113.8317	$113.83	$113.85	$113.80
Purchase #4	$174.43	11.272%	$194.0917	$194.09	$194.10	$194.10
Purchase #5	$93.55	11.487%	$104.2961	$104.30	$104.30	$104.30
Purchase #6	$56.42	7.421%	$60.6069	$60.61	$60.60	$60.60
Purchase #7	$150.66	4.105%	$156.8446	$156.84	$156.85	$156.80
7 purchase totals =	$696.90		$757.8421	$757.84	$757.85	$757.80