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	$190.39	5.663%	$201.1718	$201.17	$201.15	$201.20
Purchase #2	$168.64	10.656%	$186.6103	$186.61	$186.60	$186.60
Purchase #3	$154.76	6.482%	$164.7915	$164.79	$164.80	$164.80
Purchase #4	$125.54	9.636%	$137.637	$137.64	$137.65	$137.60
Purchase #5	$125.29	13.221%	$141.8546	$141.85	$141.85	$141.90
Purchase #6	$19.46	8.368%	$21.0884	$21.09	$21.10	$21.10
Purchase #7	$96.31	13.463%	$109.2762	$109.28	$109.30	$109.30
7 purchase totals =	$880.39		$962.4298	$962.43	$962.45	$962.50