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	$170.45	4.611%	$178.3094	$178.31	$178.30	$178.30
Purchase #2	$34.50	4.459%	$36.0384	$36.04	$36.05	$36.00
Purchase #3	$83.57	8.827%	$90.9467	$90.95	$90.95	$90.90
Purchase #4	$47.32	9.654%	$51.8883	$51.89	$51.90	$51.90
Purchase #5	$73.48	5.430%	$77.47	$77.47	$77.45	$77.50
Purchase #6	$204.58	3.622%	$211.9899	$211.99	$212.00	$212.00
Purchase #7	$248.51	13.440%	$281.9097	$281.91	$281.90	$281.90
7 purchase totals =	$862.41		$928.5524	$928.56	$928.55	$928.50