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	$118.53	13.522%	$134.5576	$134.56	$134.55	$134.60
Purchase #2	$56.85	11.255%	$63.2485	$63.25	$63.25	$63.20
Purchase #3	$227.27	6.171%	$241.2948	$241.29	$241.30	$241.30
Purchase #4	$201.39	7.534%	$216.5627	$216.56	$216.55	$216.60
Purchase #5	$187.83	6.123%	$199.3308	$199.33	$199.35	$199.30
Purchase #6	$81.63	4.427%	$85.2438	$85.24	$85.25	$85.20
Purchase #7	$66.77	5.317%	$70.3202	$70.32	$70.30	$70.30
7 purchase totals =	$940.27		$1,010.5584	$1,010.55	$1,010.55	$1,010.50