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	$127.72	12.782%	$144.0452	$144.05	$144.05	$144.00
Purchase #2	$132.90	10.838%	$147.3037	$147.30	$147.30	$147.30
Purchase #3	$163.32	9.789%	$179.3074	$179.31	$179.30	$179.30
Purchase #4	$150.67	9.337%	$164.7381	$164.74	$164.75	$164.70
Purchase #5	$141.71	7.842%	$152.8229	$152.82	$152.80	$152.80
Purchase #6	$160.58	11.820%	$179.5606	$179.56	$179.55	$179.60
Purchase #7	$28.52	6.185%	$30.284	$30.28	$30.30	$30.30
7 purchase totals =	$905.42		$998.0619	$998.06	$998.05	$998.00