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	$110.45	12.273%	$124.0055	$124.01	$124.00	$124.00
Purchase #2	$70.25	9.104%	$76.6456	$76.65	$76.65	$76.60
Purchase #3	$94.32	9.807%	$103.57	$103.57	$103.55	$103.60
Purchase #4	$229.43	11.824%	$256.5578	$256.56	$256.55	$256.60
Purchase #5	$42.43	3.377%	$43.8629	$43.86	$43.85	$43.90
Purchase #6	$232.57	11.247%	$258.7271	$258.73	$258.75	$258.70
Purchase #7	$167.76	9.392%	$183.516	$183.52	$183.50	$183.50
7 purchase totals =	$947.21		$1,046.8849	$1,046.90	$1,046.85	$1,046.90