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	$67.78	7.208%	$72.6656	$72.67	$72.65	$72.70
Purchase #2	$72.91	7.552%	$78.4162	$78.42	$78.40	$78.40
Purchase #3	$131.79	9.320%	$144.0728	$144.07	$144.05	$144.10
Purchase #4	$17.35	4.503%	$18.1313	$18.13	$18.15	$18.10
Purchase #5	$39.71	3.572%	$41.1284	$41.13	$41.15	$41.10
Purchase #6	$182.57	10.488%	$201.7179	$201.72	$201.70	$201.70
Purchase #7	$92.81	5.743%	$98.1401	$98.14	$98.15	$98.10
7 purchase totals =	$604.92		$654.2723	$654.28	$654.25	$654.20