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	$13.90	3.347%	$14.3652	$14.37	$14.35	$14.40
Purchase #2	$37.31	7.565%	$40.1325	$40.13	$40.15	$40.10
Purchase #3	$159.65	7.211%	$171.1624	$171.16	$171.15	$171.20
Purchase #4	$74.75	10.211%	$82.3827	$82.38	$82.40	$82.40
Purchase #5	$135.91	5.817%	$143.8159	$143.82	$143.80	$143.80
Purchase #6	$47.72	9.871%	$52.4304	$52.43	$52.45	$52.40
Purchase #7	$211.52	5.240%	$222.6036	$222.60	$222.60	$222.60
7 purchase totals =	$680.76		$726.8927	$726.89	$726.90	$726.90