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	$126.82	3.705%	$131.5187	$131.52	$131.50	$131.50
Purchase #2	$152.71	13.748%	$173.7046	$173.70	$173.70	$173.70
Purchase #3	$73.43	8.658%	$79.7876	$79.79	$79.80	$79.80
Purchase #4	$238.33	10.278%	$262.8256	$262.83	$262.85	$262.80
Purchase #5	$179.34	9.728%	$196.7862	$196.79	$196.80	$196.80
Purchase #6	$81.35	12.497%	$91.5163	$91.52	$91.50	$91.50
Purchase #7	$169.69	4.126%	$176.6914	$176.69	$176.70	$176.70
7 purchase totals =	$1,021.67		$1,112.8304	$1,112.84	$1,112.85	$1,112.80