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	$169.26	11.598%	$188.8908	$188.89	$188.90	$188.90
Purchase #2	$99.29	9.706%	$108.9271	$108.93	$108.95	$108.90
Purchase #3	$94.58	6.659%	$100.8781	$100.88	$100.90	$100.90
Purchase #4	$186.79	3.804%	$193.8955	$193.90	$193.90	$193.90
Purchase #5	$27.84	13.266%	$31.5333	$31.53	$31.55	$31.50
Purchase #6	$173.92	13.591%	$197.5575	$197.56	$197.55	$197.60
Purchase #7	$241.53	9.553%	$264.6034	$264.60	$264.60	$264.60
7 purchase totals =	$993.21		$1,086.2857	$1,086.29	$1,086.35	$1,086.30