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	$57.25	8.786%	$62.28	$62.28	$62.30	$62.30
Purchase #2	$96.75	5.351%	$101.9271	$101.93	$101.95	$101.90
Purchase #3	$156.31	5.529%	$164.9524	$164.95	$164.95	$165.00
Purchase #4	$160.97	4.681%	$168.505	$168.51	$168.50	$168.50
Purchase #5	$68.27	5.866%	$72.2747	$72.27	$72.25	$72.30
Purchase #6	$37.59	4.817%	$39.4007	$39.40	$39.40	$39.40
Purchase #7	$177.74	12.206%	$199.4349	$199.43	$199.45	$199.40
7 purchase totals =	$754.88		$808.7748	$808.77	$808.80	$808.80