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	$210.39	9.141%	$229.6217	$229.62	$229.60	$229.60
Purchase #2	$231.38	4.252%	$241.2183	$241.22	$241.20	$241.20
Purchase #3	$48.79	12.458%	$54.8683	$54.87	$54.85	$54.90
Purchase #4	$211.44	7.157%	$226.5728	$226.57	$226.55	$226.60
Purchase #5	$110.73	12.811%	$124.9156	$124.92	$124.90	$124.90
Purchase #6	$30.65	8.205%	$33.1648	$33.16	$33.15	$33.20
Purchase #7	$102.86	6.383%	$109.4256	$109.43	$109.45	$109.40
7 purchase totals =	$946.24		$1,019.7871	$1,019.79	$1,019.70	$1,019.80