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	$101.53	9.361%	$111.0342	$111.03	$111.05	$111.00
Purchase #2	$74.55	10.726%	$82.5462	$82.55	$82.55	$82.50
Purchase #3	$193.72	4.720%	$202.8636	$202.86	$202.85	$202.90
Purchase #4	$246.32	4.225%	$256.727	$256.73	$256.75	$256.70
Purchase #5	$30.71	10.266%	$33.8627	$33.86	$33.85	$33.90
Purchase #6	$54.41	4.870%	$57.0598	$57.06	$57.05	$57.10
Purchase #7	$248.59	11.369%	$276.8522	$276.85	$276.85	$276.90
7 purchase totals =	$949.83		$1,020.9457	$1,020.94	$1,020.95	$1,021.00