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	$105.75	8.496%	$114.7345	$114.73	$114.75	$114.70
Purchase #2	$33.38	3.531%	$34.5586	$34.56	$34.55	$34.60
Purchase #3	$240.42	9.605%	$263.5123	$263.51	$263.50	$263.50
Purchase #4	$63.65	6.619%	$67.863	$67.86	$67.85	$67.90
Purchase #5	$175.56	3.346%	$181.4342	$181.43	$181.45	$181.40
Purchase #6	$143.67	12.157%	$161.136	$161.14	$161.15	$161.10
Purchase #7	$168.58	6.171%	$178.9831	$178.98	$179.00	$179.00
7 purchase totals =	$931.01		$1,002.2217	$1,002.21	$1,002.25	$1,002.20