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	$102.64	10.548%	$113.4665	$113.47	$113.45	$113.50
Purchase #2	$169.31	3.417%	$175.0953	$175.10	$175.10	$175.10
Purchase #3	$78.85	8.516%	$85.5649	$85.56	$85.55	$85.60
Purchase #4	$69.38	4.326%	$72.3814	$72.38	$72.40	$72.40
Purchase #5	$19.65	9.422%	$21.5014	$21.50	$21.50	$21.50
Purchase #6	$179.41	9.695%	$196.8038	$196.80	$196.80	$196.80
Purchase #7	$217.31	8.608%	$236.016	$236.02	$236.00	$236.00
7 purchase totals =	$836.55		$900.8293	$900.83	$900.80	$900.90