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	$175.59	11.682%	$196.1024	$196.10	$196.10	$196.10
Purchase #2	$133.36	3.858%	$138.505	$138.51	$138.50	$138.50
Purchase #3	$239.30	11.836%	$267.6235	$267.62	$267.60	$267.60
Purchase #4	$238.41	11.167%	$265.0332	$265.03	$265.05	$265.00
Purchase #5	$139.55	6.560%	$148.7045	$148.70	$148.70	$148.70
Purchase #6	$35.29	11.709%	$39.4221	$39.42	$39.40	$39.40
Purchase #7	$72.84	8.331%	$78.9083	$78.91	$78.90	$78.90
7 purchase totals =	$1,034.34		$1,134.2990	$1,134.29	$1,134.25	$1,134.20