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	$184.43	6.274%	$196.0011	$196.00	$196.00	$196.00
Purchase #2	$218.82	6.813%	$233.7282	$233.73	$233.75	$233.70
Purchase #3	$37.77	9.273%	$41.2724	$41.27	$41.25	$41.30
Purchase #4	$82.84	7.498%	$89.0513	$89.05	$89.05	$89.10
Purchase #5	$38.61	7.775%	$41.6119	$41.61	$41.60	$41.60
Purchase #6	$101.65	6.462%	$108.2186	$108.22	$108.20	$108.20
Purchase #7	$189.59	10.184%	$208.8978	$208.90	$208.90	$208.90
7 purchase totals =	$853.71		$918.7813	$918.78	$918.75	$918.80