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	$70.62	11.479%	$78.7265	$78.73	$78.75	$78.70
Purchase #2	$25.87	5.445%	$27.2786	$27.28	$27.30	$27.30
Purchase #3	$191.61	3.558%	$198.4275	$198.43	$198.45	$198.40
Purchase #4	$94.40	7.455%	$101.4375	$101.44	$101.45	$101.40
Purchase #5	$105.63	11.550%	$117.8303	$117.83	$117.85	$117.80
Purchase #6	$193.98	10.630%	$214.6001	$214.60	$214.60	$214.60
Purchase #7	$64.95	12.226%	$72.8908	$72.89	$72.90	$72.90
7 purchase totals =	$747.06		$811.1913	$811.20	$811.30	$811.10