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	$172.85	7.546%	$185.8933	$185.89	$185.90	$185.90
Purchase #2	$100.71	10.273%	$111.0559	$111.06	$111.05	$111.10
Purchase #3	$112.75	8.483%	$122.3146	$122.31	$122.30	$122.30
Purchase #4	$158.88	7.477%	$170.7595	$170.76	$170.75	$170.80
Purchase #5	$164.69	11.638%	$183.8566	$183.86	$183.85	$183.90
Purchase #6	$93.71	4.872%	$98.2756	$98.28	$98.30	$98.30
Purchase #7	$93.41	9.497%	$102.2811	$102.28	$102.30	$102.30
7 purchase totals =	$897.00		$974.4366	$974.44	$974.45	$974.60