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	$204.75	3.149%	$211.1976	$211.20	$211.20	$211.20
Purchase #2	$111.30	3.594%	$115.3001	$115.30	$115.30	$115.30
Purchase #3	$157.65	5.473%	$166.2782	$166.28	$166.30	$166.30
Purchase #4	$139.77	5.732%	$147.7816	$147.78	$147.80	$147.80
Purchase #5	$99.37	12.529%	$111.8201	$111.82	$111.80	$111.80
Purchase #6	$110.70	9.683%	$121.4191	$121.42	$121.40	$121.40
Purchase #7	$78.56	4.780%	$82.3152	$82.32	$82.30	$82.30
7 purchase totals =	$902.10		$956.1119	$956.12	$956.10	$956.10