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	$210.25	13.340%	$238.2974	$238.30	$238.30	$238.30
Purchase #2	$77.90	5.638%	$82.292	$82.29	$82.30	$82.30
Purchase #3	$144.65	13.842%	$164.6725	$164.67	$164.65	$164.70
Purchase #4	$36.40	12.871%	$41.085	$41.09	$41.10	$41.10
Purchase #5	$56.88	11.752%	$63.5645	$63.56	$63.55	$63.60
Purchase #6	$151.55	11.191%	$168.51	$168.51	$168.50	$168.50
Purchase #7	$155.65	8.180%	$168.3822	$168.38	$168.40	$168.40
7 purchase totals =	$833.28		$926.8036	$926.80	$926.80	$926.90