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	$95.52	3.232%	$98.6072	$98.61	$98.60	$98.60
Purchase #2	$250.30	8.212%	$270.8546	$270.85	$270.85	$270.90
Purchase #3	$30.70	4.458%	$32.0686	$32.07	$32.05	$32.10
Purchase #4	$50.49	4.727%	$52.8767	$52.88	$52.90	$52.90
Purchase #5	$14.51	7.871%	$15.6521	$15.65	$15.65	$15.70
Purchase #6	$132.72	10.787%	$147.0365	$147.04	$147.05	$147.00
Purchase #7	$81.77	10.361%	$90.2422	$90.24	$90.25	$90.20
7 purchase totals =	$656.01		$707.3379	$707.34	$707.35	$707.40