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	$155.85	11.557%	$173.8616	$173.86	$173.85	$173.90
Purchase #2	$179.62	8.429%	$194.7602	$194.76	$194.75	$194.80
Purchase #3	$176.78	11.211%	$196.5988	$196.60	$196.60	$196.60
Purchase #4	$162.36	11.765%	$181.4617	$181.46	$181.45	$181.50
Purchase #5	$74.37	9.248%	$81.2477	$81.25	$81.25	$81.20
Purchase #6	$177.81	7.331%	$190.8453	$190.85	$190.85	$190.80
Purchase #7	$135.89	7.827%	$146.5261	$146.53	$146.55	$146.50
7 purchase totals =	$1,062.68		$1,165.3014	$1,165.31	$1,165.30	$1,165.30