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	$181.58	12.279%	$203.8762	$203.88	$203.90	$203.90
Purchase #2	$20.59	3.787%	$21.3697	$21.37	$21.35	$21.40
Purchase #3	$49.65	6.798%	$53.0252	$53.03	$53.05	$53.00
Purchase #4	$53.42	13.531%	$60.6483	$60.65	$60.65	$60.60
Purchase #5	$86.85	3.437%	$89.835	$89.84	$89.85	$89.80
Purchase #6	$184.86	6.404%	$196.6984	$196.70	$196.70	$196.70
Purchase #7	$198.69	10.724%	$219.9975	$220.00	$220.00	$220.00
7 purchase totals =	$775.64		$845.4503	$845.47	$845.50	$845.40