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	$144.68	4.783%	$151.6	$151.60	$151.60	$151.60
Purchase #2	$133.57	6.670%	$142.4791	$142.48	$142.50	$142.50
Purchase #3	$79.45	3.292%	$82.0655	$82.07	$82.05	$82.10
Purchase #4	$169.85	3.264%	$175.3939	$175.39	$175.40	$175.40
Purchase #5	$157.62	11.600%	$175.9039	$175.90	$175.90	$175.90
Purchase #6	$55.38	11.154%	$61.5571	$61.56	$61.55	$61.60
Purchase #7	$37.96	13.807%	$43.2011	$43.20	$43.20	$43.20
7 purchase totals =	$778.51		$832.2006	$832.20	$832.20	$832.30