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	$93.81	7.466%	$100.8139	$100.81	$100.80	$100.80
Purchase #2	$160.27	6.802%	$171.1716	$171.17	$171.15	$171.20
Purchase #3	$188.79	9.307%	$206.3607	$206.36	$206.35	$206.40
Purchase #4	$37.33	10.715%	$41.3299	$41.33	$41.35	$41.30
Purchase #5	$134.49	4.782%	$140.9213	$140.92	$140.90	$140.90
Purchase #6	$147.58	11.331%	$164.3023	$164.30	$164.30	$164.30
Purchase #7	$234.98	11.541%	$262.099	$262.10	$262.10	$262.10
7 purchase totals =	$997.25		$1,086.9987	$1,086.99	$1,086.95	$1,087.00