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	$94.34	10.740%	$104.4721	$104.47	$104.45	$104.50
Purchase #2	$56.38	9.760%	$61.8827	$61.88	$61.90	$61.90
Purchase #3	$76.37	4.426%	$79.7501	$79.75	$79.75	$79.80
Purchase #4	$202.81	12.142%	$227.4352	$227.44	$227.45	$227.40
Purchase #5	$65.67	8.173%	$71.0372	$71.04	$71.05	$71.00
Purchase #6	$202.28	5.534%	$213.4742	$213.47	$213.45	$213.50
Purchase #7	$123.39	3.230%	$127.3755	$127.38	$127.40	$127.40
7 purchase totals =	$821.24		$885.4270	$885.43	$885.45	$885.50