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	$211.45	11.862%	$236.5322	$236.53	$236.55	$236.50
Purchase #2	$138.83	12.764%	$156.5503	$156.55	$156.55	$156.60
Purchase #3	$55.46	11.843%	$62.0281	$62.03	$62.05	$62.00
Purchase #4	$193.93	12.431%	$218.0374	$218.04	$218.05	$218.00
Purchase #5	$250.50	4.766%	$262.4388	$262.44	$262.45	$262.40
Purchase #6	$50.66	8.578%	$55.0056	$55.01	$55.00	$55.00
Purchase #7	$196.62	6.764%	$209.9194	$209.92	$209.90	$209.90
7 purchase totals =	$1,097.45		$1,200.5118	$1,200.52	$1,200.55	$1,200.40