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	$103.93	7.355%	$111.5741	$111.57	$111.55	$111.60
Purchase #2	$68.99	4.545%	$72.1256	$72.13	$72.15	$72.10
Purchase #3	$151.56	8.372%	$164.2486	$164.25	$164.25	$164.20
Purchase #4	$239.81	13.662%	$272.5728	$272.57	$272.55	$272.60
Purchase #5	$85.37	12.554%	$96.0873	$96.09	$96.10	$96.10
Purchase #6	$186.66	3.460%	$193.1184	$193.12	$193.10	$193.10
Purchase #7	$176.56	10.822%	$195.6673	$195.67	$195.65	$195.70
7 purchase totals =	$1,012.88		$1,105.3941	$1,105.40	$1,105.35	$1,105.40