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	$182.75	5.556%	$192.9036	$192.90	$192.90	$192.90
Purchase #2	$73.37	6.672%	$78.2652	$78.27	$78.25	$78.30
Purchase #3	$132.88	7.265%	$142.5337	$142.53	$142.55	$142.50
Purchase #4	$115.28	3.621%	$119.4543	$119.45	$119.45	$119.50
Purchase #5	$114.29	8.429%	$123.9235	$123.92	$123.90	$123.90
Purchase #6	$66.82	11.231%	$74.3246	$74.32	$74.30	$74.30
Purchase #7	$154.91	4.398%	$161.7229	$161.72	$161.70	$161.70
7 purchase totals =	$840.30		$893.1278	$893.11	$893.05	$893.10