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	$196.72	13.706%	$223.6824	$223.68	$223.70	$223.70
Purchase #2	$10.30	6.177%	$10.9362	$10.94	$10.95	$10.90
Purchase #3	$131.85	12.176%	$147.9041	$147.90	$147.90	$147.90
Purchase #4	$168.63	6.444%	$179.4965	$179.50	$179.50	$179.50
Purchase #5	$43.70	9.376%	$47.7973	$47.80	$47.80	$47.80
Purchase #6	$107.80	3.801%	$111.8975	$111.90	$111.90	$111.90
Purchase #7	$25.93	6.705%	$27.6686	$27.67	$27.65	$27.70
7 purchase totals =	$684.93		$749.3826	$749.39	$749.40	$749.40