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	$153.81	9.787%	$168.8634	$168.86	$168.85	$168.90
Purchase #2	$162.30	12.167%	$182.047	$182.05	$182.05	$182.00
Purchase #3	$159.57	10.264%	$175.9483	$175.95	$175.95	$175.90
Purchase #4	$215.65	12.233%	$242.0305	$242.03	$242.05	$242.00
Purchase #5	$183.90	9.103%	$200.6404	$200.64	$200.65	$200.60
Purchase #6	$40.43	8.350%	$43.8059	$43.81	$43.80	$43.80
Purchase #7	$116.88	10.155%	$128.7492	$128.75	$128.75	$128.70
7 purchase totals =	$1,032.54		$1,142.0847	$1,142.09	$1,142.10	$1,141.90