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	$215.99	4.220%	$225.1048	$225.10	$225.10	$225.10
Purchase #2	$234.61	11.736%	$262.1438	$262.14	$262.15	$262.10
Purchase #3	$182.38	12.182%	$204.5975	$204.60	$204.60	$204.60
Purchase #4	$151.80	5.798%	$160.6014	$160.60	$160.60	$160.60
Purchase #5	$53.94	9.123%	$58.8609	$58.86	$58.85	$58.90
Purchase #6	$68.33	4.744%	$71.5716	$71.57	$71.55	$71.60
Purchase #7	$102.43	8.839%	$111.4838	$111.48	$111.50	$111.50
7 purchase totals =	$1,009.48		$1,094.3638	$1,094.35	$1,094.35	$1,094.40