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	$134.47	6.578%	$143.3154	$143.32	$143.30	$143.30
Purchase #2	$161.69	6.737%	$172.5831	$172.58	$172.60	$172.60
Purchase #3	$181.60	3.218%	$187.4439	$187.44	$187.45	$187.40
Purchase #4	$191.52	4.767%	$200.6498	$200.65	$200.65	$200.60
Purchase #5	$35.91	6.221%	$38.144	$38.14	$38.15	$38.10
Purchase #6	$112.55	6.835%	$120.2428	$120.24	$120.25	$120.20
Purchase #7	$134.91	6.495%	$143.6724	$143.67	$143.65	$143.70
7 purchase totals =	$952.65		$1,006.0514	$1,006.04	$1,006.05	$1,005.90