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	$137.64	11.104%	$152.9235	$152.92	$152.90	$152.90
Purchase #2	$114.96	7.616%	$123.7154	$123.72	$123.70	$123.70
Purchase #3	$76.50	13.163%	$86.5697	$86.57	$86.55	$86.60
Purchase #4	$51.42	11.859%	$57.5179	$57.52	$57.50	$57.50
Purchase #5	$133.53	8.325%	$144.6464	$144.65	$144.65	$144.60
Purchase #6	$14.54	5.802%	$15.3836	$15.38	$15.40	$15.40
Purchase #7	$154.74	12.489%	$174.0655	$174.07	$174.05	$174.10
7 purchase totals =	$683.33		$754.8220	$754.83	$754.75	$754.80