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	$207.59	10.811%	$230.0326	$230.03	$230.05	$230.00
Purchase #2	$72.68	8.109%	$78.5736	$78.57	$78.55	$78.60
Purchase #3	$97.64	4.387%	$101.9235	$101.92	$101.90	$101.90
Purchase #4	$238.39	3.386%	$246.4619	$246.46	$246.45	$246.50
Purchase #5	$104.48	4.337%	$109.0113	$109.01	$109.00	$109.00
Purchase #6	$140.46	13.870%	$159.9418	$159.94	$159.95	$159.90
Purchase #7	$46.41	11.715%	$51.8469	$51.85	$51.85	$51.80
7 purchase totals =	$907.65		$977.7916	$977.78	$977.75	$977.70