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	$38.34	7.830%	$41.342	$41.34	$41.35	$41.30
Purchase #2	$169.53	9.382%	$185.4353	$185.44	$185.45	$185.40
Purchase #3	$190.28	3.115%	$196.2072	$196.21	$196.20	$196.20
Purchase #4	$132.83	6.404%	$141.3364	$141.34	$141.35	$141.30
Purchase #5	$171.93	12.191%	$192.89	$192.89	$192.90	$192.90
Purchase #6	$201.75	5.524%	$212.8947	$212.89	$212.90	$212.90
Purchase #7	$17.46	6.103%	$18.5256	$18.53	$18.55	$18.50
7 purchase totals =	$922.12		$988.6312	$988.64	$988.70	$988.50