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	$105.72	5.172%	$111.1878	$111.19	$111.20	$111.20
Purchase #2	$98.88	10.841%	$109.5996	$109.60	$109.60	$109.60
Purchase #3	$154.86	6.458%	$164.8609	$164.86	$164.85	$164.90
Purchase #4	$70.81	3.281%	$73.1333	$73.13	$73.15	$73.10
Purchase #5	$47.86	4.666%	$50.0931	$50.09	$50.10	$50.10
Purchase #6	$7.36	4.259%	$7.6735	$7.67	$7.65	$7.70
Purchase #7	$179.89	9.438%	$196.868	$196.87	$196.85	$196.90
7 purchase totals =	$665.38		$713.4162	$713.41	$713.40	$713.50