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	$79.69	12.237%	$89.4417	$89.44	$89.45	$89.40
Purchase #2	$10.42	4.587%	$10.898	$10.90	$10.90	$10.90
Purchase #3	$170.32	12.665%	$191.891	$191.89	$191.90	$191.90
Purchase #4	$171.82	3.348%	$177.5725	$177.57	$177.55	$177.60
Purchase #5	$225.82	9.246%	$246.6993	$246.70	$246.70	$246.70
Purchase #6	$129.61	10.583%	$143.3266	$143.33	$143.35	$143.30
Purchase #7	$31.80	5.581%	$33.5748	$33.57	$33.55	$33.60
7 purchase totals =	$819.48		$893.4039	$893.40	$893.40	$893.40