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	$156.32	8.453%	$169.5337	$169.53	$169.55	$169.50
Purchase #2	$203.81	5.541%	$215.1031	$215.10	$215.10	$215.10
Purchase #3	$168.29	10.861%	$186.568	$186.57	$186.55	$186.60
Purchase #4	$16.83	9.365%	$18.4061	$18.41	$18.40	$18.40
Purchase #5	$209.46	3.555%	$216.9063	$216.91	$216.90	$216.90
Purchase #6	$111.51	9.657%	$122.2785	$122.28	$122.30	$122.30
Purchase #7	$123.67	3.138%	$127.5508	$127.55	$127.55	$127.60
7 purchase totals =	$989.89		$1,056.3465	$1,056.35	$1,056.35	$1,056.40