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	$167.29	11.604%	$186.7023	$186.70	$186.70	$186.70
Purchase #2	$91.33	8.777%	$99.346	$99.35	$99.35	$99.30
Purchase #3	$134.54	12.184%	$150.9324	$150.93	$150.95	$150.90
Purchase #4	$12.59	10.539%	$13.9169	$13.92	$13.90	$13.90
Purchase #5	$151.66	12.511%	$170.6342	$170.63	$170.65	$170.60
Purchase #6	$109.35	12.773%	$123.3173	$123.32	$123.30	$123.30
Purchase #7	$56.69	11.190%	$63.0336	$63.03	$63.05	$63.00
7 purchase totals =	$723.45		$807.8827	$807.88	$807.90	$807.70