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	$192.53	3.309%	$198.9008	$198.90	$198.90	$198.90
Purchase #2	$43.99	3.809%	$45.6656	$45.67	$45.65	$45.70
Purchase #3	$209.52	7.152%	$224.5049	$224.50	$224.50	$224.50
Purchase #4	$103.52	8.520%	$112.3399	$112.34	$112.35	$112.30
Purchase #5	$230.36	13.778%	$262.099	$262.10	$262.10	$262.10
Purchase #6	$228.42	4.147%	$237.8926	$237.89	$237.90	$237.90
Purchase #7	$62.74	9.765%	$68.8666	$68.87	$68.85	$68.90
7 purchase totals =	$1,071.08		$1,150.2694	$1,150.27	$1,150.25	$1,150.30