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	$64.95	11.337%	$72.3134	$72.31	$72.30	$72.30
Purchase #2	$83.76	8.157%	$90.5923	$90.59	$90.60	$90.60
Purchase #3	$187.48	11.621%	$209.2671	$209.27	$209.25	$209.30
Purchase #4	$164.93	10.492%	$182.2345	$182.23	$182.25	$182.20
Purchase #5	$179.94	9.724%	$197.4374	$197.44	$197.45	$197.40
Purchase #6	$221.54	12.196%	$248.559	$248.56	$248.55	$248.60
Purchase #7	$56.55	3.777%	$58.6859	$58.69	$58.70	$58.70
7 purchase totals =	$959.15		$1,059.0896	$1,059.09	$1,059.10	$1,059.10