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	$129.90	3.497%	$134.4426	$134.44	$134.45	$134.40
Purchase #2	$116.43	13.300%	$131.9152	$131.92	$131.90	$131.90
Purchase #3	$155.78	10.296%	$171.8191	$171.82	$171.80	$171.80
Purchase #4	$95.59	3.589%	$99.0207	$99.02	$99.00	$99.00
Purchase #5	$140.51	12.218%	$157.6775	$157.68	$157.70	$157.70
Purchase #6	$137.29	5.174%	$144.3934	$144.39	$144.40	$144.40
Purchase #7	$234.32	12.808%	$264.3317	$264.33	$264.35	$264.30
7 purchase totals =	$1,009.82		$1,103.6002	$1,103.60	$1,103.60	$1,103.50