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	$89.53	12.782%	$100.9737	$100.97	$100.95	$101.00
Purchase #2	$248.81	5.360%	$262.1462	$262.15	$262.15	$262.10
Purchase #3	$161.90	3.630%	$167.777	$167.78	$167.80	$167.80
Purchase #4	$218.81	12.503%	$246.1678	$246.17	$246.15	$246.20
Purchase #5	$147.84	3.781%	$153.4298	$153.43	$153.45	$153.40
Purchase #6	$83.72	6.866%	$89.4682	$89.47	$89.45	$89.50
Purchase #7	$107.59	4.591%	$112.5295	$112.53	$112.55	$112.50
7 purchase totals =	$1,058.20		$1,132.4922	$1,132.50	$1,132.50	$1,132.50