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	$118.58	7.285%	$127.2186	$127.22	$127.20	$127.20
Purchase #2	$75.61	3.658%	$78.3758	$78.38	$78.40	$78.40
Purchase #3	$56.97	10.796%	$63.1205	$63.12	$63.10	$63.10
Purchase #4	$186.28	5.269%	$196.0951	$196.10	$196.10	$196.10
Purchase #5	$104.96	8.487%	$113.868	$113.87	$113.85	$113.90
Purchase #6	$42.87	11.618%	$47.8506	$47.85	$47.85	$47.90
Purchase #7	$41.67	10.426%	$46.0145	$46.01	$46.00	$46.00
7 purchase totals =	$626.94		$672.5431	$672.55	$672.50	$672.60