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	$144.92	13.596%	$164.6233	$164.62	$164.60	$164.60
Purchase #2	$166.88	12.874%	$188.3641	$188.36	$188.35	$188.40
Purchase #3	$212.46	3.738%	$220.4018	$220.40	$220.40	$220.40
Purchase #4	$73.30	13.867%	$83.4645	$83.46	$83.45	$83.50
Purchase #5	$239.95	13.782%	$273.0199	$273.02	$273.00	$273.00
Purchase #6	$50.56	8.390%	$54.802	$54.80	$54.80	$54.80
Purchase #7	$190.83	10.764%	$211.3709	$211.37	$211.35	$211.40
7 purchase totals =	$1,078.90		$1,196.0465	$1,196.03	$1,195.95	$1,196.10