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	$162.75	5.516%	$171.7273	$171.73	$171.75	$171.70
Purchase #2	$175.42	5.552%	$185.1593	$185.16	$185.15	$185.20
Purchase #3	$232.85	10.845%	$258.1026	$258.10	$258.10	$258.10
Purchase #4	$146.90	4.863%	$154.0437	$154.04	$154.05	$154.00
Purchase #5	$111.76	11.678%	$124.8113	$124.81	$124.80	$124.80
Purchase #6	$249.26	9.724%	$273.498	$273.50	$273.50	$273.50
Purchase #7	$130.79	7.623%	$140.7601	$140.76	$140.75	$140.80
7 purchase totals =	$1,209.73		$1,308.1023	$1,308.10	$1,308.10	$1,308.10