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	$132.42	11.264%	$147.3358	$147.34	$147.35	$147.30
Purchase #2	$119.83	11.351%	$133.4319	$133.43	$133.45	$133.40
Purchase #3	$142.43	8.747%	$154.8884	$154.89	$154.90	$154.90
Purchase #4	$228.33	3.550%	$236.4357	$236.44	$236.45	$236.40
Purchase #5	$127.50	12.705%	$143.6989	$143.70	$143.70	$143.70
Purchase #6	$73.81	6.416%	$78.5456	$78.55	$78.55	$78.50
Purchase #7	$167.78	13.852%	$191.0209	$191.02	$191.00	$191.00
7 purchase totals =	$992.10		$1,085.3572	$1,085.37	$1,085.40	$1,085.20