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	$133.31	11.175%	$148.2074	$148.21	$148.20	$148.20
Purchase #2	$40.26	5.627%	$42.5254	$42.53	$42.55	$42.50
Purchase #3	$42.26	10.108%	$46.5316	$46.53	$46.55	$46.50
Purchase #4	$57.27	10.144%	$63.0795	$63.08	$63.10	$63.10
Purchase #5	$37.85	9.274%	$41.3602	$41.36	$41.35	$41.40
Purchase #6	$129.25	11.528%	$144.1499	$144.15	$144.15	$144.10
Purchase #7	$102.93	10.307%	$113.539	$113.54	$113.55	$113.50
7 purchase totals =	$543.13		$599.3930	$599.40	$599.45	$599.30