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	$130.26	4.475%	$136.0891	$136.09	$136.10	$136.10
Purchase #2	$94.76	8.177%	$102.5085	$102.51	$102.50	$102.50
Purchase #3	$236.96	13.120%	$268.0492	$268.05	$268.05	$268.00
Purchase #4	$168.52	3.314%	$174.1048	$174.10	$174.10	$174.10
Purchase #5	$73.55	6.670%	$78.4558	$78.46	$78.45	$78.50
Purchase #6	$168.86	6.223%	$179.3682	$179.37	$179.35	$179.40
Purchase #7	$11.34	13.724%	$12.8963	$12.90	$12.90	$12.90
7 purchase totals =	$884.25		$951.4719	$951.48	$951.45	$951.50