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	$40.71	12.678%	$45.8712	$45.87	$45.85	$45.90
Purchase #2	$97.92	4.443%	$102.2706	$102.27	$102.25	$102.30
Purchase #3	$159.36	5.684%	$168.418	$168.42	$168.40	$168.40
Purchase #4	$137.53	5.115%	$144.5647	$144.56	$144.55	$144.60
Purchase #5	$101.97	11.226%	$113.4172	$113.42	$113.40	$113.40
Purchase #6	$175.59	3.680%	$182.0517	$182.05	$182.05	$182.10
Purchase #7	$201.59	8.349%	$218.4207	$218.42	$218.40	$218.40
7 purchase totals =	$914.67		$975.0141	$975.01	$974.90	$975.10