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	$209.89	8.182%	$227.0632	$227.06	$227.05	$227.10
Purchase #2	$197.57	9.592%	$216.5209	$216.52	$216.50	$216.50
Purchase #3	$164.45	7.690%	$177.0962	$177.10	$177.10	$177.10
Purchase #4	$111.29	12.190%	$124.8563	$124.86	$124.85	$124.90
Purchase #5	$181.69	8.210%	$196.6067	$196.61	$196.60	$196.60
Purchase #6	$223.86	9.698%	$245.5699	$245.57	$245.55	$245.60
Purchase #7	$65.83	3.540%	$68.1604	$68.16	$68.15	$68.20
7 purchase totals =	$1,154.58		$1,255.8736	$1,255.88	$1,255.80	$1,256.00