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	$31.34	13.710%	$35.6367	$35.64	$35.65	$35.60
Purchase #2	$172.86	3.870%	$179.5497	$179.55	$179.55	$179.50
Purchase #3	$127.55	9.280%	$139.3866	$139.39	$139.40	$139.40
Purchase #4	$23.73	5.635%	$25.0672	$25.07	$25.05	$25.10
Purchase #5	$100.45	6.111%	$106.5885	$106.59	$106.60	$106.60
Purchase #6	$159.96	13.313%	$181.2555	$181.26	$181.25	$181.30
Purchase #7	$196.69	7.289%	$211.0267	$211.03	$211.05	$211.00
7 purchase totals =	$812.58		$878.5109	$878.53	$878.55	$878.50