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	$157.39	5.855%	$166.6052	$166.61	$166.60	$166.60
Purchase #2	$73.44	12.749%	$82.8029	$82.80	$82.80	$82.80
Purchase #3	$72.34	4.569%	$75.6452	$75.65	$75.65	$75.60
Purchase #4	$158.88	8.458%	$172.3181	$172.32	$172.30	$172.30
Purchase #5	$96.42	6.577%	$102.7615	$102.76	$102.75	$102.80
Purchase #6	$137.41	6.604%	$146.4846	$146.48	$146.50	$146.50
Purchase #7	$86.41	3.690%	$89.5985	$89.60	$89.60	$89.60
7 purchase totals =	$782.29		$836.2160	$836.22	$836.20	$836.20