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	$211.84	6.274%	$225.1308	$225.13	$225.15	$225.10
Purchase #2	$25.46	12.577%	$28.6621	$28.66	$28.65	$28.70
Purchase #3	$210.76	9.867%	$231.5557	$231.56	$231.55	$231.60
Purchase #4	$101.42	6.368%	$107.8784	$107.88	$107.90	$107.90
Purchase #5	$116.77	5.705%	$123.4317	$123.43	$123.45	$123.40
Purchase #6	$138.51	11.595%	$154.5702	$154.57	$154.55	$154.60
Purchase #7	$241.52	13.391%	$273.8619	$273.86	$273.85	$273.90
7 purchase totals =	$1,046.28		$1,145.0908	$1,145.09	$1,145.10	$1,145.20