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	$168.32	3.686%	$174.5243	$174.52	$174.50	$174.50
Purchase #2	$51.95	6.783%	$55.4738	$55.47	$55.45	$55.50
Purchase #3	$100.61	12.171%	$112.8552	$112.86	$112.85	$112.90
Purchase #4	$199.97	7.130%	$214.2279	$214.23	$214.25	$214.20
Purchase #5	$14.64	5.797%	$15.4887	$15.49	$15.50	$15.50
Purchase #6	$160.83	11.428%	$179.2097	$179.21	$179.20	$179.20
Purchase #7	$20.96	4.469%	$21.8967	$21.90	$21.90	$21.90
7 purchase totals =	$717.28		$773.6763	$773.68	$773.65	$773.70