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	$77.39	4.115%	$80.5746	$80.57	$80.55	$80.60
Purchase #2	$88.95	9.721%	$97.5968	$97.60	$97.60	$97.60
Purchase #3	$195.45	6.471%	$208.0976	$208.10	$208.10	$208.10
Purchase #4	$122.48	12.308%	$137.5548	$137.55	$137.55	$137.60
Purchase #5	$207.34	7.435%	$222.7557	$222.76	$222.75	$222.80
Purchase #6	$119.42	6.354%	$127.0079	$127.01	$127.00	$127.00
Purchase #7	$210.60	7.813%	$227.0542	$227.05	$227.05	$227.10
7 purchase totals =	$1,021.63		$1,100.6416	$1,100.64	$1,100.60	$1,100.80