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	$234.75	6.233%	$249.382	$249.38	$249.40	$249.40
Purchase #2	$43.38	4.533%	$45.3464	$45.35	$45.35	$45.30
Purchase #3	$44.94	6.762%	$47.9788	$47.98	$48.00	$48.00
Purchase #4	$218.72	4.249%	$228.0134	$228.01	$228.00	$228.00
Purchase #5	$139.49	5.783%	$147.5567	$147.56	$147.55	$147.60
Purchase #6	$159.56	13.710%	$181.4357	$181.44	$181.45	$181.40
Purchase #7	$64.49	13.111%	$72.9453	$72.95	$72.95	$72.90
7 purchase totals =	$905.33		$972.6583	$972.67	$972.70	$972.60